Infotainment is high in demand, though other capabilities are enabled, including crash warning, traffic violation warning and relaying weather, traffic and other data. Vehicles share basic safety information, including their position, heading and speed.
Another capability is adaptive lighting that responds to these signals, resulting in potential for “on demand” roadway lighting systems that save energy by operating only when needed. Low-traffic roadways are considered a major application for this approach, notably roadways with low night-time traffic levels and rural roadways with no roadway lighting and high accident rates.
The Virginia Tech Transportation Institute (VTTI) recently put this idea to the test on the Virginia Smart Road, creating a responsive roadway lighting system now ready for a wide range of human-factors and other testing. The project won a 2015 Lighting Control Innovation Award of Merit as part of the Illuminating Engineering Society’s Illumination Awards. The Lighting Control Innovation Award is sponsored by the Lighting Controls Association.
The Smart Road Project
The Virginia Smart Road is a 2.2-mile stretch of road that serves as a closed test-bed for new transportation technologies. Scientists and product developers have conducted more than 20,000 hours of testing on the road since it opened.
The road features dimmable LED lighting connected via a wireless mesh network. LED lighting is instant-ON, with negligible wear and tear on the system during activation.
VTTI envisioned a customized lighting control scheme in which roadway luminaires are turned ON in front of a moving vehicle and OFF once the vehicle has passed, without affecting driving performance.
VTTI recognized dimming and response to weather and traffic conditions as additional capabilities but considered these outside the scope of the project.
The on-demand control system
The Smart Road on-demand lighting control scheme marries LED roadway luminaires, connected-vehicle technology and DSRC wireless communication. It consists of a lighting controller, or processor, receiving inputs from both vehicles and luminaires, and then acting upon luminaires using custom programming.
The vehicle continuously broadcasts its GPS location, speed and heading information. Roadside receivers pick up this information and pass it on to the lighting controller. Meanwhile, luminaire status (ON/OFF) is fed to these receivers or directly to the lighting controller. As for luminaire location, it’s stored in memory.
The lighting controller decides how far in advance of the vehicle to turn a luminaire ON and how far behind it to turn the luminaire OFF. This decisionmaking is based on a sophisticated algorithm that accounts for vehicle information and other variables such as pavement type, friction distance required to stop, and potentially visibility conditions.
Communication occurs using dedicated short-wave communication (DSRC); VTTI already had DSRC-enabled vehicle and receiver stations being used on the Smart Road. VTTI identified DSRC at 5.9 GHz as the most reliable, effective and efficient technology. However, it has a limited range of 3,280 feet.
Another option is cellular, which has a longer range (2.5-3.7 miles), though it has an end-to-end latency of 1.5 to 3.5 seconds (compared to less than 100 milliseconds for DSRC). The vehicle broadcasts via cell phone to base transceiver stations, which relays the signal to a traffic management center.
Besides these two options, VTTI recognized that other communication pathways could be used. VTTI acknowledged its DSRC-based approach requires a centrally managed system that may not be possible on roadways lacking required infrastructure. Many new roadway luminaires have individually addressable wireless controllers, which may allow a distributed scheme.
Photo by Ronald Gibbons
In “An Experimental On-Demand Roadway Lighting System,” a paper by Matthew E. Palmer, Ronald Ribbons PhD and Arash Jahangiri of VTTI, the authors concluded: “The on-demand roadway lighting system developed by VTTI is working as designed and is ready for human-factors experimentation. The system can turn luminaires ON and OFF with good performance. The latency is low enough to be unnoticeable to the vehicle operator at speeds up to 55 MPH.”
On-demand roadway lighting has the potential to produce significant energy savings while respecting traffic safety. VTTI considers its on-demand roadway lighting system to be superior to typical motion-based technologies because it is dynamic and can be tuned to the vehicle.
The researchers intend to conduct human-factors experiments and refine the system by potentially enabling the algorithm to run on multiple servers, testing at speeds higher than 55 MPH, incorporating variable luminaire spacing, addressing driver age, including motorcycles and heavy trucks, and adding dimming and response to weather factors.