Generalized Link-Cost Function and Network Design for Dedicated Truck-Platoon Lanes to Improve Energy, Pavement Sustainability, and Traffic Efficiency
The application of automation to enable truck platooning has the potential to improve fuel efficiency, but raises the need to further study impacts including the potential interactions with pavement deterioration rates. Researchers in Illinois proposed a network-design model to optimize the placement of dedicated truck-platoon lanes and user fees in a highway network, and assessed operational strategies such as configuration of truck platoons within these lanes (e.g., lateral displacements and vehicle separations). The study utilized multiple link-cost functions, mathematical models, and dynamic programming to optimize truck platoon configurations and the highway pavement rehabilitation schedule.
The interstate freeway network used in this study consisted of a total of 35 nodes and 56 demand origin-destination (O-D) pairs. Traffic data were obtained from the Illinois Roadway Information System database to simulate truck demand, based on measured truck-traffic data from 2012 at selected weigh-in-motion (WIM) sites along main interstate freeway corridors. In the analyses, the researchers made the following assumptions:
- Truck demand was scaled higher by up to an order of magnitude from 2012 levels, by assuming higher truck traffic as automation increases.
- Pavements were composed of 12-inch asphalt concrete layers over another 12-inch base layer, with a lifespan of 45 years.
- The monetary discount rate was 1.5 percent per half-year analysis period, equivalent to a 3.02 percent annual interest rate.
The results were compared to those of a network without platoon lanes and with the same traffic demand. Models were assessed for the tradeoff between fuel savings, overall travel delays, and pavement-rehabilitation costs.
- Dedicated platoon lanes could reduce the total life cycle cost (which includes energy and pavement impacts). The benchmark cost of $179.30 per truck-trip without lane conversion was 14.4 percent above the value under the optimal network scenario of $156.60 per truck-trip under the same demand levels.
- Further analysis of the cost components indicated that dedicated platoon lanes could reduce air drag costs by 14.4 percent and travel time costs by 25 percent.
- When analyzing scenarios with increasing traffic demand, the addition of driver costs resulted in an increase in cost savings from 6.5 to 49.6 percent. This result was attributed to the impacts of congestion on the regular lanes quickly dominating as demand increased, while the cost increment on the platoon lanes was marginal.
- Under a very low demand scenario with a modeled total network average annual daily traffic (AADT) of 25,000, when 28.3 percent of the network lane-miles were converted into dedicated platoon lanes, a cost reduction of 22.6 percent was estimated. This cost reduction was estimated to increase up to 78.4 percent with an increase in total demand level to a network AADT of 250,000.
- If the lane conversion cost could be reduced to be almost negligible with advanced technology, converting 54 percent of network lane-miles to dedicated platoon lanes could reduce system-wide costs by 25 percent.
- In a scenario where lane conversion was costly, the analysis found an optimal cost reduction of 14.88 percent when converting 23.28 percent of the network lane-miles to dedicated platoon lanes.