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What is it?
- Variable message signs (VMS), highway advisory radio
(HAR), variable speed limit signs (VSL), traffic sensors, and traffic
management centers (TMC) are ITS technologies that monitor and control
traffic in adverse weather conditions.
- Most ITS technologies that control traffic in adverse
road conditions are integrated with other weather-related ITS technologies
(i.e. they have weather forecasting or road maintenance capabilities).
Key Results
- VMS are the most widely used traffic control device
because they are highly visible.
- Drivers prefer VMS to Highway Advisory Radio (HAR)
because of low interest level in unadorned HAR traffic weather reports.
- Vehicle control systems like Weather-related use of
Intelligent Speed Adaptation (WISA) were very effective at controlling
vehicle speeds in poor road weather conditions.
Benefits
- Warning devices like VMS lead to fewer weather-related
road accidents.
- Traffic control devices like Weather-Related Intelligent
Speed Adaptation (WISA) are generally successful at lowering mean speeds
and standard deviation, which in turn result in fewer accidents.
Costs
- VMS: Capital Cost: 10-50k, Operation and Maintenance:
1.9-4.1k per year
- ISA: estimated cost of equipment is $226-$2265
- HAR: Capital Cost: 16-32k, Operation and Maintenance:
0.6-1k per year
- VSL: Capital Cost: 3.7-5k, Operation and Maintenance:
Not provided
Implementation and Operational Challenges
- VMS may be ambiguous or misinterpreted by drivers;
VMS may also take driver attention away from other important driving
tasks.
- Drivers may be resistant to vehicle control systems
like WISA.
Where is it implemented?
- Traffic control systems are implemented across the
United States, particularly in those areas affected by severe weather
conditions. Each state has its own system that controls traffic in different
kinds of weather conditions.
Author: Lauren Smith
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