USDOT Connected Vehicle Deployment in Wyoming Assessed Potential Fuel Consumption Reduction and Speed Limit Compliance Impacts.
Connected Vehicle Pilot Deployment Program Independent Evaluation: Environmental Impact Assessment—Wyoming
Connected Vehicle (CV) technologies have great potential for enhancing safety and mobility by leveraging advanced mobile communications to exchange information between road users and infrastructure. This study investigated the feasibility and potential benefits of implementing CV technologies to improve safety and mobility along 402 miles of Interstate 80 (I-80) in southern Wyoming, especially during severe winter weather and high wind events. To accomplish these goals, approximately 320 heavy duty commercial trucks, highway patrol vehicles, and snowplows were retrofitted with onboard units equipped with Dedicated Short-Range Communications (DSRC) that allowed vehicles to receive and broadcast CV messages. A tablet-based Human-Machine Interface (HMI) installed in the vehicles communicated information to drivers such as inclement weather warnings and advisories, recommended speeds, road closure notifications, parking/services information for trucks, vehicle restrictions, etc. Mobile weather sensors installed onto WYDOT patrol vehicles and snowplows also allowed these vehicles to transmit weather data to WYDOT’s Traffic Management Center (TMC), further improving the ability to detect and forecast road weather and pavement conditions. Using data provided by the Wyoming CV Pilot Deployment (CVPD) team, the researchers analyzed potential fuel consumption reduction benefits using simple input-output analysis and hypothetical closures in different sections of I-80. Additionally, they conducted speed limit compliance analysis, comparing before and after deployment conditions. The period from December 2016 to November 2017 represented before-deployment conditions, while January 2021 to April 2022 represented after-deployment conditions.
In this study, the input-output analysis took into account capacity and demand to estimate the total amount of delay associated with closing sections of I-80. The researchers used Average Annual Daily Traffic (AADT) values reported by the Wyoming CVPD team to estimate demand. Peak hour demand was assumed to be 10 percent of the measured AADT for the roadway section. The analysis also assumed that the closure would last for one hour. Notably, due to the low sample rate of equipped vehicles in traffic, the data available when preparing this report provided limited evidence of any direct or indirect environmental impact from the deployment. The following findings on the potential fuel consumption benefits are based on the assumption that the CV technology could successfully prevent the hypothetical one-hour closure from occurring.
For speed limit compliance analysis, two measures were used: 1) the percentage of vehicles traveling no faster than 5 miles per hour (MPH) over the posted speed limit, and 2) the percentage of vehicles traveling within (+/-) 10 MPH of the posted speed limit.
- According to the input-output analysis, fuel consumption savings could be achieved by preventing a one-hour closure in the corridor, with an estimated average of 23.8 gallons of gasoline for passenger cars and 46.5 gallons of diesel for trucks, given a 50-50 vehicle mix.
- The speed limit compliance analysis indicated that the overall percentage of drivers maintaining a speed no more than 5 mph above the posted limit improved during the later months of the after-deployment period across all weather conditions. However, a marginal improvement (3 percent) was observed during mixed weather. The percentage of vehicles maintaining a speed no more than 5 mph over the limit decreased by 14.1 percent in windy conditions and by 9.2 percent under low visibility conditions during the after-deployment period, considering both CV-equipped and unequipped vehicles.
- In terms of the percentage of vehicles traveling within a 10-mph buffer around the posted speed limit, the data showed a general shift toward more uniform speeds close to the posted limit under all weather conditions. However, this improvement could be attributed to the lack of storm conditions that led to low speed buffer results during the before-deployment period.