Use speed warning signs on dangerous curves to reduce speeds of trucks.
Colorado DOT utilizes low cost system to reduce truck speeds on mountain passes.
Date Posted

Rural ITS Toolbox

Summary Information

FHWA published guidance on the use of ITS in rural locations referred to as the Rural ITS Toolbox. The document represents best practices at the time of publication with regard to many ITS services including Emergency services; Tourism & Traveler Information; Traffic Management; Rural Transit; Crash Prevention; Operations and Maintenance; and Surface Transportation & Weather.

Information includes best practices to illustrate successful development of ITS deployment plans and also a toolbox of resources that document successful rural ITS applications.

Lessons Learned

FHWA’s Rural ITS Toolbox noted a relatively low-tech approach that was used by Colorado DOT to address mountainous terrain and high speed trucks. Colorado DOT has many highways that run through the mountains and have high truck traffic on these highways. The Colorado DOT’s experience reveals the following with regard to reducing truck speeds on dangerous curves.

  • Consider using simple radar speed detection devices in combination with dynamic message signs. To convey to trucks their current speed and to warn them of impending curves ahead which could not be safely negotiated at their current speed, use simple radar speed detection devices in combination with dynamic message signs. The relatively low cost system (estimated to cost between $25-30,000 at the time of installation in 1998) has seen dramatic results. Speed studies conducted before and after the system was installed revealed a reduction in 85th percentile truck speed from 66 to 48mph.
  • Properly calibrate the speed warning systems to ensure that the readings displayed on dynamic message signs match those displayed on speedometers in the vehicle. Inaccurate or poor information can lead to negative credibility and discontinued use of the system. Also, periodic visits to the site should be conducted to observe how the public is responding to the information.

Speed warning devices have the potential to reduce crashes and increase safety in particular in mountainous terrains as Colorado experienced. More advanced systems have been deployed in recent years that include speed enforcement through downstream traffic signals being switched to red when approaching drivers are speeding. However, this particular lesson demonstrates how a low-tech approach can result in increased safety and reduced speeds on hazardous roadways.