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Dynamic Warning Systems Enhance Safety for Cyclists and Vehicles on Scenic Roadways

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Historic and scenic roads on federal lands and in U.S. national parks are enjoyed by both motorists and cyclists. Many of these roads were designed in the early 20th century and were constructed to the design standards of the era. As park attendance has increased in recent decades, so have traffic volumes, and the types of vehicles using the roads now includes recreation vehicles, vehicles pulling trailers, and tour buses. A growing interest in cycling within national parks means more interaction between cyclists and motorists along roads with no shoulders, curves, hairpin turns, and tunnels. In an effort to decrease the number of conflicts and crashes that occur in these locations and remind all road users of safety practices needed to share the road, the NPS is using technology to improve conditions in its units. Colorado National Monument’s Rim Rock Drive is one location where a dynamic warning system has been installed to alert drivers that cyclists are on the road. The new system was part of a 2017 – 2018 roadway reconstruction project.[i]    

Project Purposes

Dynamic Warning System light and sign on Rim Rock Drive. Image courtesy National Park Service, Colorado National Monument.

Rim Rock Drive is a narrow, steep roadway carved out by the Civilian Conservation Corps in the 1930s. The drive is 23 miles long, includes three tunnels, and is considered one of the “most spectacular drives in the United States.”[ii] The road is used not only by tourists but also by vehicles accessing the town of Glade Park on the western side of the national monument. The NPS reported that the roadway averaged one documented vehicle-bicycle incident per year between 2013 and 2018, and during the peak cycling months of March through October, cyclists make up 10 percent of the traffic on the road. It’s during this peak period that the park receives, on average, one complaint per week about a near miss between a vehicle and a bicycle.[iii]

The new dynamic warning system has been placed in the uphill lane at two locations along the drive. Newer inductive loop technologies, such as those deployed at Colorado National Monument, are better able to differentiate between bicycles and motor vehicles. The loop detection system triggers a flashing light attached to a sign indicating that a bicyclist is ahead of the vehicle. In addition to serving as an alert for motorists, the warning system also serves the purpose of counting cyclists using Rim Rock Drive.


Data collection for the Rim Rock Drive warning installations will be part of an evaluation of the safety outcomes of the project. Vehicle and bicycle counts, counts of how often the system is triggered, how well the system differentiates cyclists in mixed traffic, and the number of vehicle-cycle incidents will be monitored. Surveys will evaluate driver and cyclist opinions about the system as well as operations and maintenance experiences. Reducing driver speeds and increasing the awareness of drivers are two goals of the project.[iv]


The detection warning system was funded through Federal Highway Administration (FHWA) Coordinated Technology Implementation Program funds and was part of a roadway reconstruction project in Colorado National Monument. The exact cost of the warning system is not known; however, a system to warn motorists of cyclists or pedestrians in the Knapps Hill Tunnel near Chelan, Washington, is estimated at $16,000 for installation, according to the National Center for Rural Road Safety ITS Toolkit.[v]

[i] Western Transportation Institute, Montana State University (2018). Dynamic Warning System to Alert Motorists to the Presence of Bicyclists,

[ii] National Park Service (2017). Historic Rim Rock Drive,

[iii] Hamilton, Amy (2018). Safety Upgrades at Monument. The Daily Sentinel,

[iv] Western Transportation Institute, Montana State University (2018). Dynamic Warning System to Alert Motorists to the Presence of Bicyclists,

[v] National Center for Rural Road Safety (2018).

This report was delivered to the U.S. Department of Transportation in 2020. It was primarily authored by NADO Program Manager Rachel Beyerle and NADO Associate Director Carrie Kissel. Many transportation agency staff and others assisted with this project in a variety of ways. We offer deep and heartfelt thanks to all the individuals who have provided information and images, consented to be interviewed, and offered editorial guidance in support of this research. This work is supported by the U.S. Department of Transportation under requisition number HOIT190194PR. Any opinions, findings and conclusions, or recommendations expressed in this publication are those of the authors and do not necessarily reflect the views of U.S. DOT or the NADO Research Foundation.

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