Variable Speed Limit System
Author(s): Edgar
Slidedeck Presentation Only:
Abstract:
Background/Context: Posted speed limits are the maximum legal limits under ideal conditions. However, fixed speed limits may not be a reliable indication of safe speeds as roadways are subjected to adverse weather, and poor traffic conditions.
Driving the highways of British Columbia can be challenging; often negotiating mountainous terrain with varying topography. BC highways pass through multiple climatic zones where significant changes in elevation often result in rapidly changing weather conditions along a single trip.
Aims/Objectives: The Ministry of Transportation and Infrastructure commissioned the Rural Highway Safety and Speed Review (July 2014). This study identified three BC highway corridors that are particularly affected by changing and adverse weather conditions:
*Sea to Sky Highway 99: Squamish to Whistler (30 km)
*Coquihalla Highway 5: Portia Interchange to former Toll Plaza (40 km)
*Trans-Canada Highway 1: Sicamous to Revelstoke (30 km)
The study recommended that these corridors would benefit from a Variable Speed Limit System (VSLS)to inform motorists of adverse weather conditions and automatically alter speed limits, in real-time, at any point along a corridor.
Methods/Targets: Benefits of the VSLS are felt by the travelling public and a variety of other stakeholders alike. The primary benefit of this system is to the travelling public where varying regulatory speeds help to reduce speed-related traffic incidents during inclement weather. Real-time road condition information has been made available across each corridor. Using the same infrastructure, similar information is disseminated to the travelling public using the Ministry's driver-information systems, including DriveBC, and Dynamic Message Signs (DMS). Commercial vehicles, and local regular road users benefit from improved safety. Out-of-town drivers, not familiar with problem areas for adverse weather, benefit from reduced speeds along with advanced notification of road conditions.
Ministry staff benefit from additional real-time and archival data, gathered by the VSLS, to make operational decisions. Maintenance Contractors benefit from the increased density of pavement temperature and condition data, and web cam images to aid in their operational decision making.
In addition to improving safety, the VSLS provides more information for the Royal Canadian Mounted Police (RCMP) enabling them to provide more targeted and effective enforcement, as well as providing evidentiary information as and when required for legal challenges.
Results/Activities: The VSLS measures road-weather and traffic conditions then transmits that data to the Ministry's Advanced Transportation Management System (ATMS) at the Regional Transportation Management Centre (RTMC). The ATMS then displays the updated speed limits on electronic signs along the same corridors. Speed limit reductions normally occur due to adverse weather conditions or traffic incidents. These systems use a variety of technologies to measure weather, road conditions, and traffic. Technologies utilized for the B.C. VSLS include:
*Dynamic Message Signs (DMS
*Variable Speed Limit Signs
*Pavement Condition, Temperature and Visibility Sensors
*Traffic Detection Radar
*PTZ Web Cameras
*Dataloggers
Intelligent Transportation System (ITS) components are located at 53 VSLS sites along a total of 100 km of highway.
The ATMS collects real-time data from each site, analyzes the data, and recommends a speed limit. The system presents the recommended speeds for each highway segment, for acceptance by an operator, based on the lowest speed recommended by the two subsystems.
The VSLS has been designed to support future full automation without the requirement for RTMC Official acceptance of changes to the variable speed limit signs.
Discussion/Deliverables: The VSLS is a large, complex system with multiple hardware and software subsystems. Innovative solutions developed for this project include:
*Development of unique business logic
*Fully-automated and distributed control strategies.
*Robust verification of traffic and road-weather data.
* Integration of multiple subsystems, with a variety of sensor information, to form a complete and comprehensive system.
*Optimization of data-processing algorithms to ensure real-time system response and to filter out spurious data.
*Provision of a system management dashboard for monitoring and decision making.
*Store and forward strategies to ensure continuity of incoming sensor data.
*Parallel dissemination of real-time information to support external, public-facing driver-information systems.