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.

November 2001
Glenwood Canyon,Colorado,United States

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Lesson 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.

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Rural ITS Toolbox

Author: Deeter, D., H. M. Zarean, and D. Register

Published By: U.S. DOT Federal Highway Administration

Source Date: November 2001

EDL Number: 13477

Other Reference Number: FHWA-OP-01-030

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Lesson Contacts

Lesson Contact(s):

Aimee Flannery, Ph.D., P.E.
George Mason University

Lesson Analyst:

Firoz Kabir


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Benefits From This Source

In Colorado, a downhill truck speed warning system installed on a curved section of I-70 reduced 85th percentile truck speeds by 27 percent.

Costs From This Source

A bicycle safety system was installed for $5,000 at a tunnel near Chelan, Washington.

A Minnesota integrated communications system project to share application of ITS across transportation, public safety, and transit agencies cost just over $1.5 million.

A pedestrian safety system was deployed in downtown Boulder, Colorado; total project cost ranged from $8,000 to $16,000.

A variable speed limit system consisting of multiple ITS components and covering 40 miles over the Snoqualmie Pass in Washington was designed and implemented for $5 million.

Animal warning system deployed in the Greater Yellowstone Rural Intelligent Transportation Systems (GYRITS) corridor at a cost of $3,800 per site.

Colorado DOT deployed a truck speed warning system in Glenwood Canyon at a cost ranging from $25,000 to $30,000.

During a pilot project Minnesota State Patrol vehicles were equipped with an accident investigation system at a cost of $8,000 to $10,000 per vehicle.

Emergency preemption equipment was deployed at several intersections in British Columbia, Canada at a cost of $4,000 (Canadian) per intersection.

The cost to equip a police vehicle in Dane County, Wisconsin for coordinated interagency incident response was $8,000 to $10,000.

Lessons From This Source

Provide traveler information in rural areas to allow for good travel decisions in inclement weather and construction season.

Use speed warning signs on dangerous curves to reduce speeds of trucks.

Lesson ID: 2005-00075