Tran2020 Martin Ledant10 Mar. 08 200368526

Discussion of the influence that transport has on land use and development, withreference to:

(a) the impact of investment in new transport infrastructure; and(b) the effects of reductions in transport capacity.

INTRODUCTION

It is considered that transport caninfluence economic development bycontrolling the cost of movement. Themechanisms by which this assumption isverified are multiple and complex. Forexample, lower cost of movement caninduce lower cost of production, improvedvalue of inaccessible land for growth, andhave substantial social returns (SACTRA,1996).

Thus, for transport policies andinvestments to induce development theyshould try to reduce the total cost ofmovement to society. However, theimpacts of such attempts can have multipledimensions that are not always accountedfor. Indeed, if the price of travel can beestimated quite easily in monetary terms,car travel imposes a variety of externalcosts to society, not directly borne by theuser (Murphy and Delucchi, 1998). Forinstance, users don’t usually pay for roadconstruction and maintenance, the cost ofcongestion, air pollution or otherenvironmental damage (table 1).

Those externalities tend to increasewith volume of traffic, which is itselfcorrelated to growth in income and in thedemand for transport of goods and people.However, evidence show that traffic hasbeen growing faster than economy,

implying declining transport systemefficiency. Thus, the same amount ofeconomic utility became more costly tosociety.

This might be explained by the fact thatplanners and politicians didn’t consider thefull extent of the processes. Indeed, mostinvestments and policies relied on whatmodels were able to tell. It appears nowthat important feedbacks were not alwaystaken into account in models (Hills, 1996and Littman, 2007).

To induce development, any policiesthat intend to influence the money cost ofcar use or public transport fares mustensure that external costs to society are todiminish as a result (SACTRA, 1996). Thusthey must fully account for the feedbacksthat are lacking in certain models.

The benefits and costs of differenttransport policies are discussed in thefollowing paragraphs. The two alternativesof increasing or decreasing road capacityand the importance of land use policy willbe discussed. Note that some of theconclusions lack empirical background andremain quite conceptual.

Tran2020 Martin Ledant10 Mar. 08 200368526

INCREASE IN ROAD CAPACITY

Previously, authorities have tried tosolve congestion problems by increasingroad network capacity. To relieve thenetwork, new roads were built or existingones managed more efficiently. (Younes,1993). However, the assumption that roadimprovement generates traffic has nowbecome obvious to many people (Coombe,1996) and the effectiveness of the “moreroads” policies has started to bequestioned.

Investment in more transportinfrastructure reduces the cost of travel onparts of a network. An improvement intravel cost usually generates traffic. Thisgenerated traffic can be of different types:resulting from diverted travel and resultingfrom induced travel; and can happen on ashort or longer time period.

In the short term, traffic is generatedbecause users change their behavioursfollowing new possibilities offered to them.A change in route or time only results indiverting the traffic and therefore has noimpact on its growth. When trips becomemore frequent, done with private ratherthan public transport, or to access moreremote destinations, the road improvementinduces traffic that wasn’t there before.

In the long term, even if processes areslower to occur, and may therefore beaffected by factors other than roadimprovement, they can have durable effecton traffic. Decreased demand for publictransport forces a lower servicing and inturn, a positive feedback on private car use.But more importantly, improved accessallows development in new places andtherefore affects land use pattern. Inparticular, highway capacity expansionstimulates lower-density, urban fringedevelopment, and increases the amount oftravel needed to reach those services.Those types of land use, as they don’tallow sustainable public transportamenities, have an additive effect on theshift towards private car use.

Road improvement which reducescongestion in the short term attracts

additional peak-period trips. In the longterm further growth is limited by rising costsof congestion untill a new equilibrium isreached.

In the short term, user travel costs arereduced. Travel externalities are as well,since traffic is more fluid, less time wastedand less pollution is generated. But whilegenerated traffic grows, and aprogressively consistent part is composedof induced traffic, the final effect of the roadimprovement is an inflated external cost tosociety (Litman, 2007).

Is this always true?Goodwin (1996) gathered a large

amount of evidence from various casestudies to examine the impact of extra roadcapacity on traffic growth. He concludesthat it is hard to dispute that extra roadcapacity increases volume of road traffic. Intypical congested urban area, half the newcapacity is filled within five years by trafficthat wouldn’t otherwise occur, and on alonger term the new capacity is saturatedanyway (Litman, 2007).

Nevertheless, the character andamount of induced traffic depends heavilyon the conditions in which the roadexpansion takes place. These include: pre-existing congestion, elasticity to pricechanges and the nature and size of thescheme Coombe (1998).

On the other hand, Younes (1993)points out that that new road building isn’talways followed by worsening conditionsand can still be effective in urban area if itis conjugated with efficient transport andland use policy. Sometimes, roads mustbe built in order to create a coherenttransport network thereby servicing theeconomy. But road space must beprotected from invasion by the “inefficient”car and instead allocated to alternativetransport modes.

Tran2020 Martin Ledant10 Mar. 08 200368526

DECREASE IN ROAD CAPACITY

To make his point, Younes highlightsthe case of several German cities in whicha good compromise to have been found.High capacity highways connect andbypass centres, while in urban cores carcapacity is reduced and public transportimproved and extended.

By reducing the road capacity for carsand subsequently rising travel costs, it ispossible to remove a certain amount oftraffic from the roads (Litman, 2007). Astraffic goes down, the external costs oftransport tend do as well. However, thisreduction in traffic might have negativeimpact on the economy as part of thedemand is no longer fulfilled. Thus, thecost incurred to the economy mayeventually cancel out the benefit gainedfrom reduction in the overall external costof transport to society.

But if the space taken from private carsis assigned to public transport or othermodes such as bicycling or walking, thosemodes can then become more reliable.This, in turn, boosts demand andfurthermore removes cars from the streets(Younes, 1993). If this is achieved whileobtaining the same amount of economicutility, the transportation efficiency isimproved.

However, such a scheme isn’tachievable without a subsequentintelligent land use policy. New roadconstructions can promote urban sprawland therefore increased need for caruse. Those investments that canpotentially favour the economy mustbe accompanied by land useregulations which promote optimalurban densities.

Newman et al. (1991) showedthat the relation between petrol use

per capita and density was exponential (fig1.). Especially in cities under 30 people/ha:not only are the distances longer for alltypes of journeys, but other modes thanautomobile are not possible and this haspositive feedback on car use, explainingthe exponential trend.

CONCLUSION

This was given as an example of theevidence that smart urban planning canresult in more efficient transportationsystems. On the other hand, transportpolicies can result in inefficient land usepatterns generating transport-induceddisbenefits to society. We looked at theeffect of increasing/reducing road capacitywith regard to potential development.Neither of them seemed to produceabsolute benefits to society if they were notcoupled with intelligent land use andtransport regulation.

Word Count: 1283

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