Problem: Speeding is a significant threat to public safety and warrants priority attention
The management of speed through appropriate speed limits is an essential element of highway safety. The Manual on Uniform Traffic Control Devices (MUTCD) recommends that speed limits be set within 8.05 km/h (5 mi/h) of the 85th percentile speed. The MUTCD also specifies other factors (e.g pedestrian activity and crash history) to consider but does not provide guidance on how to account for these factors. Because procedures for setting speed limits are subjective, speed limits may be established that are inconsistent and ineffective in managing speed and crash risk.
Solution: USLIMITS is a Web-based expert advisor system designed to assist practitioners in determining appropriate speed limits in speed zones
USLIMITS is a user friendly, logical, and objective approach for setting credible, safer, enforceable, and consistent speed limits.
USLIMITS calculates the appropriate speed limit for a section of road based on the information input by the practitioner:
Type of surrounding development.
Access frequency (e.g., the number of access points, driveways, intersections, and traffic signals).
Road function (e.g., traffic movement versus access to abutting properties).
Road characteristics (e.g., divided or undivided, number of lanes, sight restrictions, and roadside hazards).
Freeway conditions and important high-speed road characteristics (e.g., interchange spacing, annual average daily traffic (AADT), and shoulders).
Existing vehicle operating speeds.
Any special conditions existing on the road section (e.g., adverse alignment and parking).
Putting It in Perspective
Speeding is a significant threat to public safety and warrants priority attention. Nationally, over 30 percent (13,000 plus deaths) of all traffic fatalities annually are classified as speed related. These tragic and senseless deaths are only a small part of the total safety picture—in additional hundreds of thousands Americans receive life-altering injures as a resulted of speed-related traffic crashes.
The output from USLIMITS includes a recommended speed and a list of issues that might be further investigated.
USLIMITS is limited to determining appropriate speed limits in speed zones. USLIMITS does not address work zone speed limits, school zone speed limits, or variable speed limits that change based on traffic and weather conditions.
Successful Applications: Implementing USLIMITS based on effectiveness of other speed zone advisors
The first version of USLIMITS was based on expert speed zone advisors used by many Australian state road authorities. Version 2 of USLIMITS, released in June 2007, is based on U.S. experts. As of 2007, there were registered users of USLIMITS in 20 State DOTs, 10 county public works departments, 25 cities, and 5 law enforcement agencies.
National Deployment Statement
USLIMITS has the potential to reduce the number and severity of speed-related traffic crashes.
National Deployment Goal
Success is the reduction in the number and severity of speed-related traffic crashes.
A short-time goal is to have at least 100 users of USLIMITS in State and local agencies, including six focus states, and refinements based on user feedback completed by the end of 2008.
An intermediate goal is for USLIMITS to be adopted by the Institute of Transportation Engineers as a recommended practice for setting speed limits by 2010
National Deployment Status
The U.S. DOT conducted a series of pilot workshops for State and local agencies to provide platforms for researchers, engineers, law enforcement, educators and policy makers to address speed-setting and enforcement issues. Building on the success of these workshops, the U.S. DOT has developing a Speed Management Workshop Guide and is offering Facilitator training, so that these successful workshops can be replicated in individual states and communities. This system focuses on developing and evaluating improved engineering methods for setting rational speed limits, reducing conflicts associated with large differences in ravel speeds, and adapting travel speeds to desired levels.
USLIMITS is key to the successful achievement of the setting realistic and supportable speed limits.
Two webinairs were conducted to describe and demonstrate USLIMITS2.
UNC to host USLIMITS for one year following completing of NHCRP 3-68.
FHWA Office of Safety is currently providing funding to HSRC to provide maintenance and technical support for USLIMITS2. FHWA has specifically budgeted funds in FY 08 for technical support of version 2, including web hosting, refinement and minor enhancements suggested by users. FHWA is also providing staff hours and funding to promote the deployment and dissemination this technology. A MRT flyer was prepared and debuted at the 2008 TRB meeting. Since then copies have been provided the FHWA field offices, other Federal, State, and county meetings.
In addition, presentations and demonstrations have on USLIMITS have been made at meetings with FHWA, NHTSA, State, cities, ad counties, National Forest Service, Tribes, BIA, and Governor's safety commission.
A video conference was conducted on March 25 by WASHTO-X. A more detail video conference is planned for the Fall of 2008.
USLIMITS has been added to the Low Cost Safety Improvements Workshop, Road Safety Audits, and Pedestrian Safety Workshops
At this time, USLIMITS has been described and demonstrated to over 40 States. The States' descriptions and demonstration will be expanded to all States by the end of 2008.
The FHWA continue to deploy this technology to Federal, State, and local agencies though the Region, State and local speed management training workshops, webinars, conference, and on-site meetings.
USLIMITS is also being promoted as a tool in the implementation of the States' Strategic Highway Safety Plans.
A more formal marketing plan is being developed to further advance and accelerate USLIMITS2 use.
A session on Speed Management will be provided to the Safety and Operations Meeting in Baltimore, MD this summer.
Phase of Deployment
PHASE III-Delivery Activities
The benefits of USLIMITS are
USLIMITS will be of particular benefit to local communities and agencies that do not have ready access to engineers with speed limit setting expertise. For experienced engineers, USLIMITS can provide an objective second opinion and increase confidence in speed limit setting decisions.
To learn more about AASHTO-Technology Implementation Group's approved technologies, visit http://tig.transportation.org.
For More Information Contact:
K. Craig Allred
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