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Increased peak period congestion causes the peak to spread. The travel time impact of congestion is mitigated for some travelers, but the inconvenience of traveling at a less preferred time also has a cost. Alternatively, increases in highway supply narrow the peak. This reduces the travel time savings, but it generates a benefit for those traveling closer to their preferred times. This benefit from roadway supply increases has been ignored in practical applications, largely due to the difficulty of quantifying the effect. This paper reports on an attempt to quantify the peak narrowing effect of increased highway supply. For the morning commute, the model estimates that each 1% increase in lane-miles per thousand population results in workers departing from home about 0.06-0.09% closer to the peak time.

The increased traffic congestion along urban arterials has prompted the need to examine and implement innovative ways to accommodate the traffic. Some potential alternatives are the use of unconventional left turn treatments, prohibition of left turns at the intersection, and rerouting of them at a U-turn point beyond the intersection. This study examined the implementation of median U-turns along an urban principal arterial in Lexington, Kentucky. Traffic simulation was utilized to evaluate different alternatives including signal optimization, addition of through traffic lanes, and implementation of median U-turns in two stages. Based on the analysis, median U-turn strategies proved to be a more efficient tool for traffic management along this arterial than simply adding a lane in each direction. The median U-turns showed significant improvements in all operating measures of the arterial and average delay was the measure that improved the most at all intersections. Reducing delays by 25% and peak hour travel times by 15% are achieved without adding new lanes. Instead of initiating a costly construction program, traffic can be controlled in an innovative manner that makes better use of the existing infrastructure. [ABSTRACT FROM AUTHOR]

This paper quantifies impacts of various types resulting from traffic calming measures. Descriptive statistics on speed, volume, and collisions before and after traffic calming are derived from hundreds of studies. Using the same data sets, simple impact models are estimated. While impacts are case-specific, traffic calming measures generally reduce speeds, volumes, and collisions, in keeping with program objectives. [ABSTRACT FROM AUTHOR]

Public sector efforts to cope with traffic congestion have met with limited success, and congestion problems are likely to grow worse as urban areas continue to grow and Americans remain attached to driving alone. This study explores the characteristics of urban commuters in Washington state in order to cast light on why some people have switched from driving alone to some alternative mode of commuting. What factors—internal to their beliefs and values and external in their context for making decisions about commute trip modes of travel—distinguish switchers from single-occupancy-vehicle commuters? The study also assesses the influence of the Washington State Commuter Trip Reduction program on switchers and on commuter mode choices, more generally. [ABSTRACT FROM AUTHOR]

This article explores the meaning of congestion on highway-type rural and suburban facilities, such as tollways and freeways, and develops congestion thresholds, above which it will be necessary to add lanes to specific sections of these facilities. The study originated from the need for the development of a tender for a major tollway facility in Israel. It was necessary to clearly identify the conditions at which the flow could be termed "congested," in the sense of lower levels of service, dense flows, and tense driving conditions. Several congestion measures for the defined purpose were explored. In the end, density of flow and the resulting flow rate were found to be the most appropriate measures. Based on the measures selected, specific thresholds were developed for four-and six-lane rural and suburban sections. The measures presented are dependent primarily on the percentage of heavy vehicles. It is assumed that the conditions of the facility are "ideal," meaning a high design speed, level terrain, and wide lanes and shoulders. An example is presented and evaluated of the estimation of a nonlinear growth curve for a rural section of a tollway facility and the approximate time at which the congestion threshold will be crossed. [ABSTRACT FROM AUTHOR]

Several state, regional and local governments now are studying congestion pricing and are especially concerned with public reactions to the concept. This article analyzes the results of public opinion polls on congestion pricing spanning 13 years and draws implications for analysts assessing public opinion regarding the prospects of public acceptance. This article addresses the importance of broadening and detailing congestion pricing in public polls, including attention to variations in the concept as well as plans for revenue allocation, alternative services and mitigations. It also suggests broadening assessment of equity from its usual focus on income, testing the concept in the context of highway finance and assessing both gains and losses in support with concept variations. [ABSTRACT FROM AUTHOR]

Evaluation plays a central part in the development and implementation of Congestion Management Systems (CMS) as required within Transportation Management Areas under ISTEA legislation. Specifically, a Final CMS Rule issued by the Federal Highway Administration and Federal Transit Administration states "system monitoring shall be established … to evaluate the effectiveness of implemented actions." The Rule also states, …"traditional and nontraditional systems shall be identified and evaluated based on … established performance measures. [ABSTRACT FROM AUTHOR]

Mandatory travel reduction requirements imposed by regulation at the point of employment have emerged as a policy of choice in many jurisdictions faced with the twin challenge of reducing traffic congestion and air pollution. Over 40 localities have enacted trip reduction ordinances with the aim of relieving local traffic congestion, and 10 jurisdictions are in various stages of implementing the so-called Employee Trip Reduction programs or to comply with the requirements of the Federal Clean Air Act. This article reports on recent work of two groups: the Committee on Travel Demand Management Evaluation of the Institute of Transportation Engineers, and the Working Group on the Impact of Mandatory Trip Reduction Requirements of the Business Transportation Council.

The discomfort and dangers experienced on Rome's crowded street led Julius Cesar to issue a traffic ban ordering unnecessary vehicles off the streets during daylight hours. It appears that congestion continued in Rome, as it did in many other European cities, as population grew and particularly after private horse-drawn vehicles came into fashion centuries later. A recent comparison of conditions in 50 urbanized areas in the United States found that congestion appears to be getting much worse in most of the regions studied. The greatest increases occurred in Salt Lake City, utah, wher congestion increased by 31%. In addition, congestion increased by 15% to 20% in Columbus, Ohio and in Cincinnati, Ohio.