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1、1.5We live in a complex and rapidly developing world.consequently,the problems that traffic engineers are involved in evolve rapidly.Urban congestion has been a major issue for many years .given the transportation demand cycle,it is not always possible to solve congestion problems through expansion
2、of capacity .traffic engineers therefore are involve in the development of programs and strategies to manage demand in both time and space and to discourage growth where necessary,a real question is not “how much capacity is needed to handle demand? “but rather“how many vehicles and/or people can be
3、 allowed to enter congested areas within designated time periods?“Growth management is a major current issue. A number of states have legislation that ties development permits to level-of-service impacts on the highway and transportiaton system.where development will cause substantial deterioration
4、in the quality of traffic service ,either such development will be disallowed or the developer will be responsible for general highway and traffic improvement that mitigate these negative impacts.such policies are more easily dealt with in good economic times.When the economy is sluggish,the issue w
5、ill often be a clash between the desire to reduce congestion and the desire to encourage development as a means of increasing the tax base.Reconstruction of existing highway facilities also causes unique problems.the entire interstate system has been aging,and many of its facilities have required ma
6、jor reconstruction efforts.part of the problem is that reconstruction of interstate facilities receives the 90%federal subsidy,while routine maintenance on the same facility is primarily the responsibility of state and local governments.deferring routine maintenance on these facilities in favor of m
7、ajor reconstruction efforts has resulted from federal funding policies over the years.major reconstruction efforts have a substantial major burden not involved in the initial construction of these facilities maintaining traffic.it is easier to bulid a new facility in a dedicated right-of-way than to
8、 rebuild it while continuing to serve 100000 or more vehicles per day.thus,is issues of long-term and short-term construction detours as well as the diversion of traffic to alternate routes require major planning by traffic engineers.Recently,the issue of security of transportation facilities has co
9、me to the fore .the creation of facilities and processes for random and systematic inspection of trucks and other vehicles at critical locations is a major challenges ,as is securing major public transportation systems such as railroad ,airport and rapid transit systems.The list goes on and on .the
10、point is that traffic engineers cannot expect to practice their profession only in traditional ways on traditional ways on traditional projects.like any professional,the traffic engineer must be ready to face current problems and to play an important role in any situation that involves transportatio
11、n and/or traffic systems. 1.6In order to remain up to date and aware the traffic engineer must keep up with modern developments through membership and participation in professional organizations ,regular review or key periodicals,and an awareness of the latest standards and criteria for professional
12、 practice .Key professional organizations for the traffic engineer include the institute of transportation engineer(ITE),the transportation research board(TRB),the transportation group of the American society of Civi engineers(ASCE),ITS America,and others.all of these provide literature and maintain
13、 journals,and have local,regional,and national meetings.TRB is a branch of the national Academy of engineering and is a major source o research papers and reports.Like many engineering fields the traffic engineering profession has many manuals and standard references ,most of which will be referred
14、to in the chapter of this text.major references includeTraffic engineering handbook1Uniform vehicle code and model traffic ordinance2Manual on uniform traffic control devices 3Highway capacity manual4A policy on geometric design of highways an streets(the AASHTO Green Book)5A few of these have had m
15、ajor update and revisions since 2000,including references ,1,3,4 and 5.most standards such as these are updated frequently,usually on a 5-or10-years cycle,and the traffic engineer must be aware of how changes in standards,criteria,methodology,and other aspect will affect the practice of the professi
16、on. Other manuals abound and often relate to specific aspects if traffic engineering.these references document the current state of the art in traffic engineering,and those most frequently used should be part of the professionals personal library.There are also a wide variety of internet sites that are of great value to the traffic engineer.specific sites are not listed here ,as they change rapidly.all of the professional organizations,as well as equipment manufacturers,maintain web
