wider roads, more cars

Natural Resources

FORUM PERGAMON Natural Resources Forum 25 (2001) 147-155

www.elsevier.com/locate/natresfor

Wider roads, more cars Petter Naess, Martin J. H. Mogridge, Synn@ve Lyssand Sandberg

Deli1 of Development and Planning, Aalborg University, Aalborg, Denmark. E-mail: [email protected] (P. Nress)

Abstract

The transport policy currently followed in many European cities seems to be a combination of investments in public transport in order to increase, or at least maintain, its market share, and road building in order to keep up with expected trafic growth. Apparently, there is a prevalent belief among policy makers that increased road capacity in urban areas does not in itself cause any growth in car trafic worth mentioning. Such a belief neglects the simple economic theory of supply and demand, as well as more specific theories about the dynamics of trafic under congested conditions. An empirical study of commuting patterns in two transport corridors in Oslo, Norway, shows that a considerable proportion of commuters are sensitive to changes in the speed of the respective modes of transportation. The mode chosen depends to a large extent on the ratio of door-to-door travel times by car and transit. Freerjowing trafic in the road network will induce a higher proportion of commuters to travel by car. Conversely, faster public transport will reduce the proportion of car commuters, but the effects of such improvements will be offset if road capacity is simultaneously increased. In addition to the relative speeds of car and transit, the parking conditions at the workplace are of great importance to the choice of transport mode. 0 2001 United Nations. Published by Elsevier Science Ltd. All rights reserved.

Keywords: Road capacity; Public transport; Modal split; Congestion; Induced travel

1. New goals, old measures

During recent decades, many European governments have formulated targets for limiting car traffic in urban areas and changing the modal split towards a higher share of public and non-motorized modes. The background for these aims is two-fold: a shift of travellers to transit, walking and biking could relieve congestion and save time spent by commuters stuck in rush hour gridlocks. A limitation of car traffic in urban areas is also cidled for in order to meet the challenges of environmental management. Automobile transport is almost completely based on fossil fuels and is an important and growing contributor to greenhouse gas emissions. In urban traffic, cars use considerably more energy than public transport (Newman and Kenworthy, 1999; Heyer and Heiberg, 1993), whereas electricity-driven transit causes virtually no local air pollution. A shift from private motoring to public transport could therefore relieve congestion as well as local and global-scale air pollution.

Government statements about the need to curb urban motoring and enhance public transit, walking and biking include a 1998 White Pnper by the British Government aiming “to create a better, more integrated transport system to tackle the problems of congestion and pollution we have inherited” (HMSO, 1998); Danish governmental objectives

of “redistributing transport to more environmentally friendly modes” (Ministry of Transport, 1993, p. 10); and Norwegian national policy provisions of coordinated land use and transport planning. According to the latter, “when the capacity of the road network is insufficient, equal consideration shall be given to alternatives other than increasing the capacity of the roads, such as, regulating the traffic, improving public transport services.” (Ministry of the Environment, 1993, p. 3).

In spite of this, considerable investments are still being channeled into road construction programmes aiming to keep up with expected growth in car traffic. In a recent UN report (UN Economic Commission for Europe, 1998), the construction of new and wider urban expressways to cope with the increasing traffic growth is cited as one of the major trends in urban spatial development. In Denmark, the length of motorways increased by 30% during the period 1990-1994 (Tengstrom, 1999). Over the next 10 years, the Danish motorway network is planned to increase by another 40% (Information, 1999). In Norway, the Highway Direc- torate has identified a need for an extra NOK 100 billion (equivalent to about US$15 billion) for road standard improvement in response to unexpectedly high traffic growth in the 1990s. This is in addition to the considerable funding already granted for road construction during the

0165-0203/01/$20.00 0 2001 United Nations. Published by Elsevier Science Ltd. All rights reserved. PII: SOl6S-O203(00)00050-7

I48 P. Nless et a/. /Natural Resources Forum 25 (2001) 147-155

next decade. About NOK 5 billion is proposed to be spent on widening the highway leading from the western suburbs of Oslo to the city centre (Aftenposten, 1998). Referring to the situation in the UK, Richardson (2000) raises doubts as to whether the proclaimed new and more sustainable transport policy will bring about any considerable or permanent change of course. Policy and decision-making is still char- acterized by a fragmented rationality that has favoured road building over other modes. Road investment appraisals are bolstered by calculations of the expected social benefits of road building-principally saving time for motonsts- while rail must prove a commercial case (Richardson, 2000).

However, quite substantial investments in rail transport have also been made in the larger urban regions of all the above-mentioned countries during recent years. In Norway, for example, a new high-speed railroad was opened in 1998 between the new international airport at Gardermoen and downtown Oslo, with a travel time of I9 min for a distance of 48 km. In Copenhagen, the city’s first metro is being constructed these days, and the decision has been made to construct a ring rail connecting the existing radial rail lines. In the largest Danish provincial cities, new local rail routes with a higher frequency of departure are underway. In London, the construction of the Jubilee Line improving access by public transport to the eastern and southeastern parts of the city may provide a good example.

The strategy currently followed by many European governments seems to be a combination of investments in public transport in urban areas in order to increase, or at least maintain, its market share, and road building in order to keep up with expected traffic growth. According to the Norwegian and Danish governments, there is no contradic- tion between the goals of limiting car traffic and increasing the market share of public transport on the one hand, and the practice of road building resulting in increased urban road capacity on the other (Ministry of Transport, Norway, 1997; Ministry of Transport, Denmark, 2000). In Norway, a white paper from the Government stated:

Various analyses indicate that [road] capacity increases in themselves do only to a modest extent contribute to traffic growth, and that they have therefore contributed substantially to relieve the problems of congestion (Ministry of Transport (Norway), 1997).

The question still remains whether such a double-edged strategy of ‘balanced’ investments in improved public transport and increased road capacity would bring about a reduction in energy use, emissions and congestion levels described in the goals stated in policy documents.

Traditionally, traffic engineers have assumed that increased road capacity in urban areas does not cause any appreciable growth in car traffic, i.e., that there is virtually no induced trufic (Noland and Lem, 2000). Model simulations of the impacts of alternative transport and land use

policies tend to support such a belief. In the beginning of the 1990s, the International Study Group on Land Use/ Transport Interactions (ISGLUTI) carried out a number of model simulations testing a wide range of urban policies, including new road construction and faster public transport (Dasgupta, 1994). Each policy alternative was tested by means of simulations carried out with 10 different simula- tion models. According to the ISGLUTT study, building a new orbital road or an inner ring road would change the modal shares only marginally, resulting in an increase in car kilometres of less than 1 % on average. A 10% increase in the central area road capacity was predicted to result in 0.5% increase in vehicle kilometres but 0.5% decrease in emissions in the city as a whole. The simulations included an alternative where the average speed of public transport was improved by 20%, combined with a reduction in the speed of car traffic by 20%. The result of this quite substantial change in the relative speeds of the two modes in favour of public transport was calculated to be a modest reduction of the share of car transport of 5.7%. However, due to the slower moving traffic on the roads, the overall carbon diox- ide emissions were found to increase by 3.2% (Dasgupta, 1994).

The underlying assumption of such model simulations is that there is a small, or even negligible, field of competition between car and public transport. If people have got a car, they will use it. Mass transit, it is assumed, is mainly for those who have not got a car at their disposal, or for those who for other reasons are not able to travel by car. Consequently, increased road capacity in congested urban areas will bring about better-flowing traffic, without in itself affecting significantly the proportions of travellers going by private and public transport. Supporters of this theory of non-interaction between automobile transport and mass transit (except for the impact of increasing car ownership) include Bly et al. (l987), Dasgupta (l994), Klaeboe (1994) and Solheim et al. (1994). Theories attri- buting a dominant influence on modal choice to lifestyle preferences of individuals, with little room for any influence from the physical structure of cities might also be grouped under this label.

2. The theory of induced travel

Contrary to the above, the second group of theories assume that there is a considerable field of competition between private and public transport in urban areas. Accord- ing to this group of theories, a high proportion of travellers choose the mode of transport they find to be most attractive with respect to speed, price, comfort, etc., and they are sensitive to changes in these factors. Increasing the capacity of roads will make the traffic flow more easily. Accordingly, the attractiveness of the car mode will increase. Road building in order to relieve congestion is therefore likely to induce more travellers to drive.

P. Nass et al. /Natural Resources Forum 25 (2001) 147-155 149

The underlying theory behind induced travel is the simple economic theory of supply and demand. When the highway capacity in urban areas increases, the time cost of travelling by car is reduced. I n particular, this is the case if there is a suppressed demand for travel due to congestion. Travel time is a major component of the variable costs experienced by motorists. When any good (in this case travel) is reduced in cost, the demand for this good increases (Noland and Lem, 2000). According to economic theory, increased road capacity is therefore likely to change travel behaviour. In the short term, the following effects are likely to occur (Downs, 1992; Noland and Lem, 2000).

Changes in the modal split, by reducing the costs of road transport but not the cost of rail transport. Changes in travelling distances, by increasing the distance that can be travelled within a given time limit. Changes in the routes chosen, by making it relatively more attractive to drive on the expanded road than on the adjacent road network. Changes in the proportion of people travelling at peak periods, by reducing the time cost and inconvenience associated with driving in the period that would, other things being equal, be most convenient in relation to the working hours.

In the longer term, road capacity increases could also be expected to induce land-use changes by making it more attractive to build in areas made more accessible due to the higher speeds on the road network, e.g. areas previously located outside an acceptable commuting distance from an employment centre.

Of these five types of effects, the attraction of traffic away from parallel minor roads will often be considered benefi- cial, as this can make residents of these streets less exposed to traffic nuisance. Seen from the perspective of the individual traveller, the other effects too might be considered positive. In terms of social costs, however, all the above eflects, except the channeling of traffic away from minor streets, may have a negative impact, in particular, from an energy perspective. Rescheduling trips from off-peak to

I cost 7

$ 1

[increase in proportion-: bycor j j

Fig. 1. The Downs-Thomson paradox. Source: Mogridge, 1997.

peak periods, increasing travelling distances, a more sprawl- ing urban developmental pattern, and shifting travellers from public transport to private motoring, all contribute to increasing the energy used for transport and related emissions. As will be argued below, there is little reason to believe that the positive effect of a more energy-efficient driving style under less congested conditions can counter- balance these negative effects. Due to induced traffic, the extended road is likely to be soon filled with cars again, thus reducing or offsetting the initial improvement i n energy efficiency of each individual vehicle. Since the number of vehicles has grown, the energy use will also be higher.

3. The Downs-Thomson paradox

In the following, we will concentrate on one of the above behavioural responses to increased road capacity in urban areas, namely the shift of travellers from public to private transport. Hypotheses put forward by Downs ( I962), Suchorzewski (1973, 1976) Thomson (1977), Mogridge (1986, 1990, 1997), Mogridge et al. (1987), Olszewski and Suchorzewski (1987) and Jansson ( 1993) provide important background information for the study presented below. The point of departure for the argument of these researchers is the fact that the consequences of increased urban traffic in terms of travel speeds are opposite for car traffic and public transport.’ Car traffic has an upward cost curve with increasing flow, while the opposite is the case for public transport. Increased car traffic will cause congestion and lower speeds on urban roads whereas higher patronage of public transport may facilitate more frequent departures (reducing waiting times). Higher patronage could also create an economic surplus, enabling the transit company to invest in faster (reducing running time) and more comfor- table vehicles.’ In other words, the collective transport operator gains economies of scale, contrary to the diseconomies of scale characterizing an increased flow of cars on the road network. The costs referred to are the perceived costs, including what is actually paid for each mode of transport, as well as time, effort, risk, inconvenience, etc. All these costs added up are called ‘generalized costs’.

If road capacity is increased, there will be less congestion-for a given amount of traffic. The cost curve of car traffic will therefore have a less steep gradient (cf. Fig. 1) . Hence, the cost curve of public transport is crossed further to the right in the figure, implying that car and mass transit are perceived to be equally attractive at a higher share of car traffic than before the road extension. However, at this higher share of car traffic, public transport has lost some of its economies of scale, and has perhaps been forced to

’ The argument mainly refers to public transport running on separate right of way.

* Higher patronage may of course also enable the transit companies to reduce fares (reducing money costs) and increase network density (reducing walking time and interchange time), though the latter may involve substantial investment if the track is fixed rail.

I50 P. Ness et al. /Natural Resources Forum 25 (2001) 147-155

compensate for this by reducing the frequency of departures, increasing the fares or cutting back on maintenance and comfort. When the situation has stabilized, the crossing of the curves therefore occurs at a higher cost level for both car traffic and public transport than before the road extension! This counter-intuitive and paradoxical conclusion has often been referred to as the Downs-Thomson paradox. In traffic comdors with a high density of cars, vacant road capacity will, according to Downs and Thomson, tend to be utilized until the traffic density on the roads has increased to a level where the attractiveness of car traffic is similar to that of public transport. If the congestion increases beyond this level, the attractiveness of car traffic will drop below that of transit and in turn cause some motorists to change to the transit mode. The traffic load on the roads will gradually stabilize at a level where car and transit are equally attractive (Downs, 1962; Thomson, 1977).

According to Mogridge (1990), studies have indicated that travel time door-to-door accounted for a large proportion, maybe two thirds, of the generalized travel costs. If the above arguments are valid, the most efficient way of increasing travel speeds of car traffic in congested urban areas will be to reduce door-to-door travel times by public transport. Increasing road capacity in congested conditions will, according to Mogridge, only increase flow, not speed, and thus be counter-productive.

This is a brief summary of the arguments of Downs, Thomson and Mogridge. Their reasoning is based on several assumptions. Firstly, they assume that a large proportion of the travellers can choose between car and public transport. For ‘captive riders’, e.g. travellers without access to a car, or commuters who need to use the car during the workday or for errands on their way to or from the workplace, the mode of transport will not be influenced by variations in the travel speeds of car and transit. Secondly, it is assumed that the travellers are ‘rational actors’ whose choice of mode is determined by what gives them the highest utility, and not by, e.g. what is most common among neighbours and fellow workers, or by ideas of what one ought to do, for example for environmental reasons. Furthermore, the theory assumes that saving travel time is conceived by the travellers to be of a high utility. The theory assumes that travel time makes up a substantial part of the ‘generalized cost of travel’, although the latter also includes a number of measurable and non-measurable features in addition to the time spent during the trip. Fourthly, it is assumed that a large proportion of those who can choose among modes, i.e. the ‘non- captive riders’, are attentive to marginal changes in the speeds of either of the modes and adjust their travel behaviour accordingly. Finally, the theory assumes that the total traffic through the transport corridor is sufficiently high so that the flow-cost curves of car and transit intersect (see Fig. 1). Obviously, the latter requirement is not met in small villages or sparsely populated rural areas.

Although theoretically compelling, clear empirical evidence about the potential behavioural characteristics of

induced travel effects from road capacity increases has so far been elusive. This is partly due to the difficulty of statistically separating the many effects that also increase the total amount of traffic and establishing clear causal relationship (Noland and Lem, 2000). However, if it can be shown that there is a clear relationship between the actual modal choices of individual commuters in a transport comdor and the relative door- to-door speeds of car and transit faced by each commuter, this would provide an empirical support of the part of the theory concerning the effects of capacity increases in terms of switch- ing between modes. In particular, this is the case if such a relationship could be shown to exist also when controlling for relevant socio-economic factors.

4. The case study

The dispute over whether increased road capacity will improve travel speeds without increasing the traffic volume is one main reason for the case study presented below. Commuting patterns among travellers in two transport comdors in Oslo have been surveyed.’ Oslo, the capital of Norway, has a population of approximately 750 000 within the continuous urban area. One of the surveyed comdors follows the heavy-rail line of the National State Railways and the highway El8 between downtown Oslo and the suburb of Asker (the NSB comdor). The other corridor follows a combined metro and open-air urban rail line from downtown Oslo to the suburb of 0steris (the gsteris comdor). In each corridor, surveys were carried out in 1995 and 1997 among a sample of respondents working in downtown Oslo and living within certain residential zones.4

Theoretically, highway capacity effects could be expected to be larger where travel time accounts for a greater fraction of the generalized costs of travel (Noland and Lem, 2000). Conversely, if the monetary costs of travel make up a high proportion of the generalized costs, more modest effects from road capacity increases could be expected. This makes the Oslo case particularly interesting. Gasoline prices in Norway are among the highest in the world. At the time the study was carried out, the price of 1 1 of gasoline was about NOK 8 (about US$1.15). In addition, Oslo is one of the few cities with an inbound toll cordon surrounding its inner parts. Among our respondents, all car commuters had to cross this ring and pay a toll on inbound trips. The toll is NOK 12 for a single trip, with a certain discount (up to approx. 35%) for drivers holding a subscription.’ Electronic checkpoints allow motorists with

Further details can be found in an English-language report (92 pages) from the study (Naess and Sandberg, 1998).

The residential zones were located at least 10 km away from the workplace zone. This implied that almost all our respondents traveled by motorized modes. In our analyses, the few persons commuting the entire distance by non-motorized modes have been excluded. ’ Some 75% of the net revenue from the tolls is used for road construction

and maintenance and only some 25% is used to support public transport.

P. N m s et al. /Natural Resources Forum 25 (2001) 147-155 151

a pass to drive straight through without delay. Travelling by public transport is also relatively expensive, with the price of one-way single tickets ranging from NOK 28 to NOK 39 (US$4.00-5.60) for the commuting distances travelled by our respondents.

The high gasoline price, thc cost of road tolls and the high public transport fares imply that the monetary costs of commuting in Oslo probably make up a higher share of the generalized travel costs than in most other cities. Theo- retically, a small influence on modal choice from differences in the travel times by car and transit could therefore be expected. In this sense, Oslo might be considered a ‘critical case’: if shorter travel time by car increases the likelihood of commuting by car i n Oslo, then such an effect will probably also exist in most other cities with peak-period congestion on the road network.

Distinct from the dominant trend in the economics literature of using aggregate data, the Oslo study used disaggre- gated data with individual travellers as its units of analysis. This provides a better understanding of how individuals respond to the conditions of road capacity and public transportation services, parking conditions etc. The questionnaire included detailed questions about the journey to work on a particulx day, as well as questions about the socio- economic status of the respondents. In addition to looking for statistical relationships i n cross-sectional data sets, we asked respondents how they would react to hypothetical changes in travel times by car or by transit, as well as to changes in transit fares. Furthermore, a before-and-after analysis was carried out among a panel of respondents in one of the corridors, where the rail service was reopened in 1996 after an intermediate period when the trains were replaced by buses due to reconstruction.

In order to investigate the extent to which the modal choice of the respondents was influenced by the door-to- door travel speeds of the respective modes, travel time ratios were calculated. The travel time ratios would vary, depend- ing on, among other factors, the walking distances to public transport stops at each end of the journey, walking distances to and from parking places, and the proportions of car journeys taking place on residential streets, the main road, and locnl streets near the workplace. For each respondent, information about door-to-door travel times by the mode of transportation actually chosen was taken directly from the questionnaire. In addition, hypothetical travel times were calculated for the mode not chosen. For the respondents who travelled by car, travel times for commuting by public transport were calculated, and for those travelling by public transport the hypothetical travel times of using the car were estimated. These calculations of hypothetical travel times were made based on the recorded times spent on segments of the journey by respondents living or working close to the respondent in question. The clustering of the workplaces and residences of the respondents within the residential zones and the downtown workplace zone made this approach possible. In addition, driving tests were carried

out in the residential and workplace segments, and walking distances to and from public transport stops were measured to improve the information on hypothetical travel times.

5. The ratio of travel times clearly influences the choice of mode

Statistical analyses of the data sets from the two corridors show a clear correlation between the door-to-door travel time ratio between car and public transport, and the actual mode of transportation chosen by the commuters. When door-to-door travel time by car is 20% shorter than by transit, the probability of commuting by car varies from 16 to 25% among the four data sets (0sterls corridor 1995 and 1997, and NSB corridor 1995 and 1997). When door-to- door travel time by car is 20% longer than by public transport, the probability of commuting by car varies from 4 to 1 1 % in the respective studies. Fig. 2 shows this relationship, based on the data from the NSB corridor in 1995. The low overall probability of commuting by car must be seen in the light that all our respondents were working in the downtown area. Studies in a number of cities have shown that the proportion of car commuters is usually considerably lower at workplaces in the city centre than at outer-area or fringe locations (see, e.g. Naess and Sandberg, 1996; Hartoft-Niel- sen, 1997; Dasgupta, 1994).

The above figures refer to simple bivariate correlations. Keeping the control variables constant at mean values, the four data sets show a difference of some 15- 20 percentage points in the probability of commuting by car between a situation where car is 20% faster than transit, compared to

0 0.5 1 1 3 2

Travel time ratio carltransit

Fig. 2. NSB corridor 1995. Probabilities of commuting by car at varying ratios of door-to-door travel times by car and by transit. Notes: Bivariate logistic regression, without controlling for other variables. N = 274 employees living in the Asker and Sandvika areas and working downtown Oslo. Sig. = 0.0000.

152 P. Ncess et ul. /Natural Resources Fr,rum 25 (2001) 147-155

a situation where the door-to-door journey by car takes 20% longer than by transit.

The ratio between the travel times of car and transit is, of course, not the only factor influencing the modal choice of the commuters. Our material shows that the modal split by car is increased by:

higher car ownership and driver’s license-holding; doing errands on the way home from work; a lower travel-time ratio; better parking conditions at the workplace; car travel expenses being paid by the employer.

On the contrary, the opposite levels would encourage use of communal transport.

As can be seen above, our analyses show that the variables that can be influenced by transport infrastructure planning- the travel time ratio and the parking supply at the workplace- exert important influences on the modal choice. Still, as one might expect, car ownership and driving license holding exerted the strongest influences. The effect of carrying out errands on the way home from work was also strong. Neither the age, sex, income level or education level of the respondents appears to exert any influence worth mentioning on the modal choice of the respondents. It should be noted, however, that the residential areas from which the respondents were drawn belong to the more affluent parts of Greater Oslo, and the average income level as well as the car ownership rate among our respondents is high.

Fig. 3 shows how the probability of travelling by car varies with the travel time ratio between car and public transport when controlling for other possible factors of influence. The probabilities referred to in the figure are among male respondents holding a driver’s license, with a high car ownership level (i.e. one car per adult household member), and who consider the parking conditions at the workplace to be good. The remaining independent variables (income level, education level, age, travel expenses paid by the employer, and errands on the way home from work) have been kept constant at mean values. Among this group of respondents, the probability of travelling by car is 40% when car and transit are equally fast from door to door (i.e. at a travel time ratio of 1.0). When the door-to- door travel time by car is only 80% of that by transit (i.e. at a travel time ratio of 0.8) the probability of travelling by car is 59%. The important implication of this difference of 19 percentage points is that when increased road capacity reduces travel time by car from a door-to-door level similar to public transport to a level 20% below, a considerable number of travellers will shift from collective to individual transport.

As mentioned above, the parking conditions at the workplace are among the factors influencing the modal choice. Keeping other investigated variables (including the travel time ratio) constant at mean values, the probability of commuting by car is 39% among respondents enjoying

x 0,8 n i

0,6 i

5 0,5 1 0 0.4 x

0.3 a m 0

’c

0 0.2

0.1 ,

0 0 5 1 1.5 2

Travel time ratio cadtransit

Fig. 3. NSB conidor 1995. Probabilities of commuting by car at varying ratios of door-to-door travel times by car and by transit. Multivariate logistic regression. Notes: Probabilities refer to male respondents holding a driver’s license, with a high car ownership level and good parking conditions at the workplace. The following variables have been kept constant at mean values: income level, educational level, age, travel expenses paid by the employer, and errands on the way home from work. N = 261 employees living in the Asker and Sandvika areas and working downtown Oslo. Sig. = 0.0000.

satisfactory parking conditions at the workplace. With poor parking conditions (i.e. scarce, expensive or non- existing parking possibilities within acceptable walking distance), the likelihood of being a car commuter is only 20%.

The above figures refer to the 1995 data of the NSB corridor. Similar effects of the travel time ratio and the parking conditions on the modal choice were found in the three other data sets (the NSB corridor 1997, and the 0sterHs corridor 1995 and 1997).

6. The respondents’ own statements indicate that travel time plays an important role

In addition to asking the respondents about their actual commuting behaviour (‘revealed preferences’), we also asked which mode of travel they would prefer if the travel times of car and public transport, respectively, were changed. The ‘stated preferences’ thus elicited show that the relationships found between modal choice and travel time ratio in cross-sectional statistical analyses are also present for the individual respondent when he or she is asked about the hypothetical choice of mode of transportation, given certain changes in the travel times of the respective modes.

In addition to the travel times of competing modes of transportation, the parking conditions, and the personal resources of the travellers (income, education, drivers’ license, car ownership etc.), transportation behaviour may also be influenced by the traveler’s lifestyle and attitudes.

P. NLESS et al. /Natural Resources Forum 25 (2001) 147-155 153

For example, the car is often considered not only a measure for movements from one place to another. To many people, the car is also a symbol of freedom or a way to express one’s affluence or esthetic taste (see, e.g. Berge, 1994; Jensen, 1997). The questionnaires of the 1995 study included open-ended questions where the respondents were asked to list the three main reasons for their actual mode of travelling on the particuku- day investigated. Taken together, the various arguments concerning time consumption made up nearly 40% of all reasons given, whereas 38% were other utility-oriented reasons. Another 7% of the reasons could be grouped under the heading of habits, while constrained options and social norms accounted for 6 and 5%, respectively. PsychologicaVexpressive reasons, e.g. references to freedom or joy of driving, made up only 3% of the reasons given.

In the 1997 survey, the respondents were asked to state the importance of a number of fixed answer categories concerning the reasons for the modal choice. This change in the setup of the questionnaire was made because the context i n which the questions were asked might perhaps draw the attention of the respondents to the time consumption aspects of the journey at the cost of other aspects. With fixed answer alternatives, the respondents were reminded about possible reasons other than just time saving. This time, too, travel time turned out to be an important factor, along with the parking conditions at the workplace. However, some other reasons were given a higher importance in 1997 than in the 1995 survey. Apart from travel time and parking conditions, the modal choice of our respondents appears to be influenced by a number of other utilitarian aspects of the journey, notably the comfort and convenience, the possibility of transporting goods or persons, and the monetary expenses of the trip. To some extent, social norms of environmental protection make up a part of the reason for choosing the public transport mode. Although very few respondents consider the journey to work as an opportunity to experience the joy of driving, the general freedom and flexibility provided by the car is emphasized quite strongly by the car commuters as a reason for their modal choice.

7. The before and after study

As mentioned earlier, we dso carried out a before and after study in the 0sterAs corridor, where the urban rail services were closed down for 10 months in 1995 and replaced with buses. We assumed that the quality of the public transport services in the 0sterAs corridor would be improved significantly after the reopening of the urban rail line. In order to estimate the influence of this expected improvement on the modal choice of the commuters, a comparison of travelling patterns before and after the reopening of the light rail line was carried out. However, because of technical and spin-off effects from construction

work on other light rail lines, the 0steris urban rail line was riddled by frequent delays after reopening. These problems had still not been overcome when the after survey was conducted. Among the respondents participating both in the before and after study (the so-called panel of respondents), there was only a modest reduction in average door- to-door travel time by transit (from 42 min in 1995 to 39 min in 1997). Among the car commuters of the 0steris corridor panel, the average travel time increased by 1 min (from 25 to 26 min from door to door). Despite the small improvement in the door-to-door speed of travelling by transit, the proportion travelling by public transport remained constant at 75%.

For the panel of respondents in the NSB comdor, the average door-to-door travel time by transit increased slightly (from 43 to 45 min), whereas the travel time by car was reduced by 2 min on average (from 34 to 32 min). In spite of the relative worsening of the travel times by transit compared to car, the proportion of transit riders increased from 81% in 1995 to 85% in 1997.

The most likely explanation for this surprising development is the fact that the parking conditions at the workplaces of many respondents also changed during the period between the before and the after study. In the panel of respondents in the 0steris corridor, the proportion with satisfactory parking conditions increased by nearly 10 percentage points, while decreasing by six percentage points in the NSB corridor. Thus, while the changes in average travel times encouraged the use of transit in the asteris corridor and commuting by car in the NSB corridor, the changes in the parking conditions at the workplace worked in the opposite direction.

8. Conclusions

Our various data sources all indicate that the relative speeds of car and public transport, measured from door- to-door, exert an important influence on the modal choices of our respondents’ journey to work. On average, our cross- sectional data indicate that road capacity expansion leading to a reduction in travel time by car from 80 to 60% of the corresponding journey by public transport (i.e. a reduction of 20 percentage points) is likely to make some 15 or 20% of the total number of respondents change their travel mode from transit to car. This finding goes to the heart of the discussion about what could be done to improve the traffic situation in the NSB corridor of Oslo. Our results clearly contradict the previously mentioned governmental state- ment that road capacity increases ”in themselves do only to a modest extent contribute to traffic growth” (see Section 1). UK studies, reported by the Standing Advisory Committee on Trunk Road Assessment (SACTRA, 1994) point in the same direction as our findings. The converse also applies i.e. that road capacity reductions reduce traffic (Bates et al., 1997; Cairns et al., 1998).

I54 P. N m s et ul. / Nuturul Resources Forum 25 (2001) 147-155

They also contradict the often-mentioned hypothesis that there is a small and negligible field of competition between public and private transport. Our studies have shown that, in the investigated corridors, the field of competition is quite large for journeys to work.

To what extent may the results of our study in the 0sterAs and NSB comdors be generalized? First, it is important to notice that the commutes investigated in the two corridors, were journeys directed towards workplaces in downtown Oslo. Compared to journeys to workplaces in outer areas of the city, the competitiveness of public transport is much higher when the workplace is located in the centre of the city (Hanssen 1993; Nzss and Sandberg 1996; Engebretsen 1996). Because a considerable proportion of the commuters in the two corridors do not work in the downtown area, our sample is likely to include a larger share of transit travellers than is the case among the commuters in the two corridors in general. Also, the residences of our respondents are clus- tered relatively close to public transport routes. In particular in the general NSB corridor, many of the commuters live at a longer distance from the railway stations than in our sample, and hence will have a lower door-to-door travel time ratio between car and transit.

The authors’ investigation is limited to journeys to work. Several studies have shown that public transport is more able to compete with the private car for such journeys than for most other travelling purposes, due to the high concentration of traffic in time and space creating the economies of scale for transit and diseconomies of scale for car traffic discussed in the beginning of the paper. If the study had included all travelling purposes in the two corridors and not been limited to journeys to work, the proportion of public transport travellers would probably have been considerably lower.

The relationship between modal choice and the door-to- door travel time ratio between car and transit is likely to be valid, even if the focus is on journey types where the general competitiveness of public transport is lower. For example, Engebretsen (1996) has investigated the journeys to work of commuters living in the southern transport corridor of Oslo. The workplaces of these commuters were scattered all over Greater Oslo, and the proportion of journeys directed towards the downtown area was thus not dominant. For more than 80% of the employees living in the southern corridor of Oslo, the door-to-door travel time by public transport was more than 1.5 times longer than by car. The proportions of transit passengers were accordingly lower than in our study. Still, the shape of the curve showing the relationship between modal choice and travel time ratio was very similar.

Based on the authors’ study of commuting patterns in the two investigated comdors in Oslo, the following main conclusions can be drawn.

There clearly exists a field of competition between car and public transport for journeys to workplaces in down-

town Oslo. The proportion of commuters sensible to changes in the speed of the respective modes of transport appears to be considerable. A number of circumstances influence the travellers’ choice of mode of transportation. However, the travel time ratio between car and public transport as well as the parking conditions prove to be important. This implies that the distribution of travellers between public and private transport is highly influenced by important elements of urban and traffic planning: road construction, investments in faster and more frequent public transport, allocation of existing road capacity to different modes of transport (e.g. bus lanes vs. lanes for ordinary car traffic), and provision of parking capacity. More free-flowing traffic in the road network will cause a higher proportion of the commuters to choose the car mode. The same applies to increased parking capacity at the workplace. Conversely, faster public transport will reduce the proportion of car commuters. Reduced road capacity slow- ing down the flow of car traffic is also likely to result in a shift of travellers from private to public transport. The same applies to reduced parking capacity.

A consequence of these conclusions is that increasing road capacity is a counter-productive strategy if the goal is to increase the share of journeys to work on public transport. For each billion spent on road construction aiming to increase the travel speeds along congested urban highways, it will be necessary to make substantial, and perhaps equally large, investments in better public transport just in order to maintain the existing modal split. If the objective is to limit energy use for transport and increase the market share of environmentally friendly modes of transport, then such ‘balanced’ investments in road building as well as transit improvement are just like stepping on the accelerator and the brake at the same time.

References

Aftenposten, 1998. 5 March. Bates, .I., Dale, M., Coombe, D., 1997. Impact of highway capacity reduc-

tions: report on modelling. MVA for London Transport Planning and the Department of the Environment, Transport and the Regions. MVA, London.

Berge, G., 1994. The battle of images; cultural conceptions of different transport modes in Oslo. Paper presented at RC 2 1 -session 6: ‘Everyday life in post-modem cities’ ISA XI11 World Congress of Sociology, Bielefelt, July 18-23. Institute of Transport Economics, Oslo.

Bly, P.H., Johnston, R.H., Webster, F.V., 1987. A panacea forroad congestion?. Traffic Engineering (28), 8-12.

Cairns, S., Hass-Klau, C., Goodwin, P., 1998. Traffic impact of highway capacity reductions: assessment of the evidence. Transport Studies Unit, University College London for London Transport Planning and the Department of the Environment, Transport and the Regions. Landor Publishing, London.

Dasgupta, M., 1994. Urban travel demand and policy impacts. Paper presented at the course, The urban environment and transport policy, at the Norwegian Institute of Technology, Trondheim. 10-12 January.

Downs, A,, 1962. The law of peak-hour expressway congestion. Traffic Quarterly (16). 393-409.

P. Nress et al. /Natural Resources Forum 25 (2001) 147-155 I55

Downs, A,, 1992. Stuck in traffic: coping with peak-hour congestion. The Brookings Institution, Washington. DC.

Engebretscn, $3.. 1996. Lokalisering, tilgjengelighet og arbeidsreiser. En analyst: av arbeidsreiser i Osloregionens sorkorridor basert p i kriteriene i ABC-systemet. (Location, accessibility and journeys to work. An analysis of commutes in the South corridor of the Oslo region based on the criteria of the ABC system.) T 0 I Working Paper 1048/1996. Institute of Transport Economics, Oslo.

Hanssen, J.U., 1993. Transportmessige virkninger av nzringsvirksomheters lokalisering. (Transportation impacts caused by the relocation of firms.) T01 Rcport 215/1993. Institute of Transport Economics, Oslo.

Hartoft-Nielsen, P., 1997. Lokalisering, transportmiddel og bystruktur. (Location, conveyance and urban structure). Byplan (6/97), 247-260.

Her Majesty’s Stationery Office (HMSO), 1998. A New Deal for transport: better for everyone. The Government’s white paper on the future of transport. Her Majesty’s Stationery Office, London.

Hoyer, K.C., Heiberg, E., 1993. Persontransport-konsekvenser for energi og miljg. Direkte og indirekte energibruk og milj~ikonsekvenser ved d ike transportmidler. (Passenger transport: energy and environmental consequences. Direct and indirect energy use and environmental consequences of different nienns oftransport) Report 1/93. Western Norway Research Center, Sogndal.

Information, 1999. 17 April. Jnnsson, J.O., 1993. Government and transport infrastructure investment.

In: Polak, J.B., Heertje, A. (Eds.). European Transport Economics. European Conference of Ministers of Transport, Paris.

Jensen, M., 1997. Benzin i blodet. Kvalitativ del. (Gasoline in the blood. Qualitative part) ALTRANS. Scientific report from DMU, no. 191. Nationd Environmental Research Institute, Roskilde, Denmark.

Kleboe, R., 1994. Konkurransellater mellom bil og kollektivtransport. Eksempler: Troms0 og Oslo/Akershus. (Fields of competition between car and public transport. The cases of Tromso and Oslo/Akershus.) T 0 I report 221/1994. Institute of Transport Economics, Oslo.

Ministry ofthe Environment (Norway). 1993. National policy provisions of coordinated land-use nnd transport planning. Ministry of the Environ- ment, Oslo.

Ministry of Transport (Denmark), 1993. Trafik 2005: Problemstillinger, mil og strategier. (Traffic 2005: Problem issues, goals and strategies.) Ministry of Transport. Copenhagen.

Ministry of Transport (Denmark), 2000. Grundlag for trafik- og milj~iplan for hovedstadsomridet. (A foundation for a plan for transport and environment in the Copenhagen areti.) http://www.trm.dk/pub/grundlag_ for-trafiklkapl .htm, June 29.

Ministry of Transport (Norway). 1997. St. meld. nr. 37 (1996-97): Norsk veg- og vegtrafikkplan 1998-2007. (Norwegian road and road traffic plan 1998-2007.) Ministry of Transport, Oslo.

Mogridge, M.J.H., 1986. Jam yesterday, jam today and jam tomorrow? (or how to improve traffic speeds in Central London) University College of London, Lunch-hour lecture, 17 October 1985. University College London, Transport Studies Group, London.

Mogn’dge, M.J.H., 1990. Travel in Towns. Jam Yesterday, Jam Today and Jam Tomorrow? Macmillan Reference Books, London.

Mogridge, M.J.H., 1997. The Self-defeating Nature of Urban Road Capa- city Policy. A Review of Theories, Disputes and Available Evidence. Transport Policy 4 ( I ) , 5-23.

Mogridge, M.J.H., Holden. D.J., Bird, J., Terzis, G.J., 1987. The Downs- Thomson paradox and the transportation planning process. International Journal of Transport Economics (14). 283-3 1 1.

Newman, P.W.G., Kenworthy, J.R., 1999. Sustainability and Cities: Over- coming Automobile Dependence. Island Press, Washington, DC/ Covelo, CA.

Noland, R.B., Lem, L.L., 2000. Induced travel: a review of recent literature and the implications for transportation and environmental policy. Paper presented at the European Transport Conference 2000. (Revised inter- net version, September 7, 2000).

Nzss, P., Sandberg, S.L., 1996. Workplace location, modal split and energy use for commuting trips. Urban Studies 33 (3), 557-580.

Nzss, P., Sandberg, S.L., 1998. Choosing the fastest mode? Travel time and modal choice in two transport comdors of Oslo. NIBR Report 1998: 15. Norwegian Institute for Urban and Regional Research, Oslo.

Olszewski, P., Suchorzewski, W., 1987. Traffic capacity of the city centre. Traffic Engineering and Control 28,336-348.

Richardson, T., 2000. Before the pendulum swings again: grounding the new transport realism. Forthcoming in Town Planning Review, 2001.

Solheim, T. et al., 1994. Kollektivt og forurensende? Miljeeffekter av i forbedre kollektivtilbudet i norske byer. (Public and polluting? Envir- onmental effects from improving the public transport services in Norwegian cities. T 0 I report 245/1994. Institute of Transport Econom- ics, Oslo.

Suchorzewski W., 1973. Principles and applicability of the integrated transportation system. In Proceedings of the UN-ECE Seminar on the role of transportation in urban planning, development and environment, Munich.

Suchorzewski, W., 1976. Planning measures to promote a balance among traffic and transportation modes with special regard to the human scale. In Proceedings of the 2nd. UN-ECE Seminar on the role of transportation in urban planning, development and environment. Washington DC.

Tengstrom, E., 1999. Towards Environmental Sustainability? A Compara- tive Study of Danish, Dutch and Swedish Transport Policies in a European Context. AldershoVBrookfield, Ashgate, USNSingaporel Sydney.

Thomson, J.M., 1977. Great Cities and their Traffic. Gollancz, London. U.K. Standing Advisory Committee on Trunk Road Assessment, 1994.

Trunk Roads and the Generation of Traffic. Her Majesty’s Stationery Office, London.

United Nations, Economic Commission for Europe (UNECE), 1998. Major Trends Characterizing Human Settlements Development in the ECE Region. United Nations, Economic Commission for Europe, Geneva.

wider roads, more cars

Documents