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In the U.S., more than 15% of average household income is spent on highway vehicle

Purchases

In the U.S. alone, in the light-vehicle maret !cars,

vans, picup trucs, and so on", as many as 1# million or more new vehicles can $e

sold annually !depending on economic conditions", which translates to over &&

$illion dollars in sales and more than a million 'o$s in manufacturing andmanufacturing-supplier industries. (dd to this the additional employment associated

with vehicle maintenance and servicing, and

more than five million U.S. 'o$s can $e tied directly to highway vehicles

)he influence of the highway economy e*tends

further to the heavy-vehiclesector as well, with more than 1.+ million 'o$s and

$illions of dollars e*pended annually $y the trucing, freight movement, and other

industries in conducting operations and e*panding, replacing

modern economies is predicated on efficient and relia$le supply chains.

Industries have $ecome increasingly dependent on their supply chains to

reduce costs and remain competitive.

most manufacturing industries today rely on just-in-time (JIT) delivery to reduceinventory-related

costs, which can $e a su$stantial percentage of total costs in many industries.

The idea of JIT deliveryis that the materials reuired for production are supplied 'ust $efore they are

needed.hile such a strategy significantly reduces inventory costs, it requiresa very high

degree of certainty that the reuired materials will $e delivered on time. If not, the

entire production process could $e adversely affected and costs could rise

dramatically.

In retail applications, effective supply chains can significantly reduce consumer

costs and ensure that a sufficient uantity of goods is availa$le to satisfy consumer

demand.

)he a$ility of highways to provide relia$le service for I) inventory control

and other supply-chain-related industrial and retail applications has made highways

critical to the function of modern economies

In the U.S., hih!ay transportation is responsi"le for rouhly #$ percent of all

petroleum consumption )his translates into a$out %& million "arrels of oil a day

In terms of emission impacts,highway transportation is responsi"lefor roughly /5

percent of U.S. greenhouse gas emissions !including over +& percent of car$on

dio*ide emissions".

0ighway transportations contri$ution to other pollutants is also su$stantial.

'ih!ay travelis responsi$le for about 35 percent of all nitrous oide

emissions !23*" and /5 percent of volatile oranic compoundemissions !43",

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$oth ma'or contri$utors to the formation of o6one. 'ih!ay travel also contri$utes

more than 5& percent of all car"on monoide!3" emissions in the U.S. and is a

major source offine particulate matter!/.5 microns or smaller, P7/.5", which is a

nown carcinoen.

8iven these num$ers, the energy and environmental impacts of highway

transportation are clearly su$stantial, and an important consideration in the designand maintenance of highway facilities and the development and implementation of

policies affecting highway transportation

It is important to eep in mind that highway transportation is part of a larger

transportation system that includes air, rail, water and pipeline transportation.

In this system, hih!ays are the dominant mode of most passenerand freiht movements.

9or passenger travel, highways account for a$out :& percent of all passenger-miles.

3n the freight side, commercial trucs accountfor a$out +; percent of the freight

ton-miles and, $ecause commercial trucs transport hiher-valuedgoods than other

modes of transportation !with the e*ception of air transportation", nearly *$ percent

of the dollar value of all oods is transported "y commercial trucs.

hile hih!aysplay a dominant role in $oth passenger and freight movement

In many applications there are critical interfaces among the various transportation

modes. 9or e*ample, many air, rail, water and pipeline freight movements involve

highway transportation at some point for their initial collection and final distri$ution.

Interfaces $etween modes, such as those at water ports, airports and rail terminals,create interesting transportation pro$lems $ut, if handled correctly, can greatly

improve the efficiency of the overall transportation system.

+f the availa"le ur"an transportationmodes !such as $us, commuter train, su$way,private vehicle, and others", private vehicles !and single-occupant private vehicles in

particular" offer an unequaled level of mo"ility.

The sinle-occupant private vehicle has$een such a dominant choice that travelers have $een willing

to pay su$stantial capital and operating costs, confront high levels of conestion, and strule !ith

parin-relatedpro$lems 'ust to have the fle*i$ility in travel departure time and destination

choices that is uniuely provided $y private vehicles.

In the last $ years, the percentage of trips taen in private vehicles has risen from slightly less than ;&

percent to over :& percent !pu$lic transit and other modes mae up the $alance".

+ver this same period, the average private-vehicle occupancyhas dropped from 1.//

to 1.&: persons per vehicle, reflecting the fact that the single-occupant vehicle has

$ecome an increasingly dominant mode of travel.

, the total num"er of fatalities per year in

the U.S. has remained unaccepta$ly high at more than +&,&&& per year.)o understand why U.S. highway fatality num$ers have not dramatically

decreased or why fatality rates !fatalities per distance driven" have not dropped more

than they have as a result of all the safety efforts, a num$er of possi$le e*planations

arise< an increase in the overall level of aressive drivin increasin levels of

disrespectfor traffic control devices !red-light and stop-sign running $eing two of the

more nota$le e*amples"= in-vehicle drivin distractions!cell phones, eating, taling

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to passengers) driver impairments!alcohol, drugs, fatigue) and poor drivin sills in

the youner and older drivin populations.

Investments in highway infrastructure have $een made continuously throughout the

/&th and /1st centuries. Such investments have understanda$ly varied over the yearsin response to need, and political and national priorities. 9or e*ample, in the U.S., an

etraordinary capital investment in hih!ays durin the %#$s and %/$s !asundertaen "y constructin the interstate hih!ay system and upradin and

constructin many other hih!ays.

)he economic and political climate that permitted

such an am$itious construction program has not $een replicated$efore or since. It is

difficult to imagine, in todays economic and political environment, that a pro'ect of

the magnitude of the interstate highway system would ever $e seriously considered.

)his is $ecause of the prohi"itive costs associated !ith land acquisition

Until the 1:;&s, vehicle technologies evolved slowly and often in response to mild

trends in the vehicle maret as opposed to an underlying trend toward technological

development. >eginning in the 1:;&s, however, three factors "ean a cycle of

unparalleled advances in vehicle technoloy that continues to this day< !1"government regulations on air uality, fuel efficiency, and vehicle-occupant safety,

!/" energy shortages and fuel-price increases, and !+" intense competition among

vehicle manufacturers !foreign and domestic". )he aggregate effect of these factors

has $een vehicle consumers that demand new technology at highly competitiveprices. 0ehicle manufacturers have found it necessary to reallocate resources and to

restructure manufacturin and inventory control processes to meet this demand. In

recent years, consumer demandand competition among vehicle manufacturers has

resulted in the widespread implementation of new technologies including

supplemental restraint systems, anti-loc "rae systems, traction control systems,

electronic sta"ility control, and a host of other applications of ne! technoloies to

improve the safety and comfort in highway vehicles. )here is little dou$t that thecom$ination of consumer demand and intense competition in the vehicle industry

will continue to spur vehicle technological innovations.

Intersection traffic signals are a familiar traffic-control technology. (t signali6ed

intersections, the trade-off $etween mo$ility and safety is $rought into sharp focus.

Procedures for developing traffic signal control plans !allocating green time toconflicting traffic movements" have made significant advances over the years. )oday,

signals at critical intersections can $e designed to respond uicly to prevailing

traffic flo!s, roups of sinals can "e coordinated to provide a smooth throuh-flo!

of traffic, and, in some cases, computers control entire net!ors of sinals.