Managing Speed Review of Current Practices for Setting and Enforcing Speed Limits -- Special Report 254 (1998) / Chapter Skim
Currently Skimming:
Chapter 5: Other Speed Management Strategies
Chapter 5: Other Speed Management Strategies
Pages 166-185
The Chapter Skim interface presents what we've algorithmically identified as the most significant single chunk of text within every page in the chapter.
Select key terms on the right to highlight them within pages of the chapter.
From page 166... ...
For example, speed limits are frequently violated on local streets in urban areas, where the level of enforcement required to achieve compliance with posted speed limits using traditional enforcement methods is prohibitively expensive. In this chapter, alternative methods for controlling speeds are briefly considered.
|
From page 167... ...
These different procedures can lead to inconsistencies among design speeds, speed limits, and driver operating speeds. Such differences are not necessarily cause for alarm.
|
From page 168... ...
considers the relationship between vehicle operating speeds and roadway geometric design elements. Model development efforts are focused on higher-speed, two-lane rural highways where inadequate consistency and continuity of design contribute to wide dispersions in driving speeds and increased crash risk.4 Models are also being developed for 2 The Netherlands has embarked on a comprehensive program to rationalize its entire road system to bring road function, use, and vehicle travel speeds into greater harmony (see discussion in Chapter 3 under the section "Application of Speed Limits")
|
From page 169... ...
The effort to achieve greater congruence between highway design and driver expectations of appropriate operating speeds clearly has potential to improve safety. However, more research, validation of model results, and better understanding of the safety benefits of alternative designs are required before the approach can be adopted as standard design practice.
|
From page 170... ...
Traffic calming treatments can be applied singly (e.g., speed humps on indi Figure 5-1 Examples of selected traffic calming techniques (Ullman 1996, 112; Ewing and Kooshian 1997, 2833)
|
From page 171... ...
Traffic calming is not considered suitable for urban arterial streets, which serve commuter and commercial traffic and carry emergency vehicles.6 Although not widely used, traffic calming techniques are also appropriate in transition areas. For example, "gateway" treatments -- a combination of road surface treatments and vertical elements, such as trees and lamp standards, to create the impression of passing through a narrowed entrance -- can be used to alert drivers on rural roads to adapt their speeds as they approach villages or more built-up suburban and urban areas.7 Many studies have documented the speed and traffic-reducing effects of traffic calming (Pharoah and Russell 1989; Fildes and Lee 1993, 6973; Loughery and Katzman 1998, 23)
|
From page 172... ...
have also noted safety benefits of traffic calming, citing large reductions in crash frequency and injury severity, although safety is not the sole objective of neighborhood traffic calming projects. In theory, lowering vehicle speeds should reduce the severity of crashes, particularly those involving pedestrians.
|
From page 173... ...
Because they require driver compliance, many operational measures (e.g., stop signs) are less effective than their physical counterparts in reducing driving speeds (Ullman 1996, 114)
|
From page 174... ...
. A curve-approach warning system, using roadside communication beacons to provide information about roadway geometry, could alert drivers to sharp curves, warning them if the vehicle is approaching at excessive speed (TRB 1998, 33)
|
From page 175... ...
Vehicle control technologies offer another level of sophistication in speed management. Conventional cruise-control systems, which are mainly used in freeway driving, already enable drivers to establish and maintain a fixed vehicle speed.
|
From page 176... ...
Where they do exist, their primary function is to provide weather advisories and appropriate speeds for hazardous conditions. Variable speed limits have been used more extensively in Europe, particularly on major motorways, for general speed management.11 They are especially well suited to address temporal changes in traffic volumes, speed, and density on urban Interstate highways.
|
From page 177... ...
. Local jurisdictions are experimenting with these devices to supplement traditional enforcement measures in problem speed locations on city streets, in neighborhoods, and in school and work zones.12 An evaluation of the effectiveness of roadside speedometers under several controlled deployment strategies (e.g., varied, intermittent, and continuous deployment, each with and without enforcement)
|
From page 178... ...
This new Intelligent Vehicle Initiative, which deemphasizes the earlier target of fully automated driving, is focused on improving highway safety (TRB 1998, 5)
|
From page 179... ...
. Previously discussed technological advances in driver information systems and vehicle control technologies could enhance the ease and speed with which information is provided to the driver and simplify some driving tasks.
|
From page 180... ...
. Many public health pro 17 Typical elements of a graduated licensing system include a mandatory supervised driv ing period, night driving curfew, limits on teenage passengers riding with a beginning driver, a freeway driving restriction, and a lower blood alcohol concentration threshold for teenagers than for adults (Status Report 1996, 12)
|
From page 181... ...
Road redesign -- and to an even greater extent traffic calming -- attempt to physically constrain driving speeds to desired levels. Traffic calming can be an effective strategy for reducing speed on some residential streets, but it is not considered suitable for major urban roads.
|
From page 182... ...
The approaches identified in this chapter offer a range of methods for controlling driving speeds. Their use is often limited to certain types of roads or settings (e.g., residential streets)
|
From page 183... ...
In Living With Traffic, Special Report 53, Australian Road Research Board, Victoria, pp.
|
From page 184... ...
Research Report CR4/94. Monash University Accident Research Centre and Australian Road Research Board Ltd., Nov., 52 pp.
|
From page 185... ...
1996. Relationship of Operating Speeds to Roadway Geometric Design Speeds.
|
Key Terms
This material may be derived from roughly machine-read images, and so is provided only to facilitate research.
More
information on Chapter Skim is available.