Truck Platooning Effects on Girder Bridges, Phase II

Connected and Automated Driving System (C/ADS)-equipped vehicles are expected to become increasingly common in the United States and elsewhere globally. To address the challenges posed by these new systems on infrastructure, the Transportation Research Board has funded NCHRP Project 20-102: Impacts of Connected Vehicles and Automated Vehicles on State and Local Transportation Agencies. This $6.5M project has produced several noteworthy products pertinent to this proposal. In particular, Project 20-102(03): Challenges to CV and AV Application in Truck Freight Operations produced NCHRP Web-Only Document 231 by Fitzpatrick et al. in 2016, and Project 20-102(07): Implications of Automation for Motor Vehicle Codes produced a 6 volume NCHRP Web-Only Document 253. Fitzpatrick et al. note that truck platooning has been studied as a means of reducing aerodynamic drag for many years, noting work ranging from a study by California Partners for Advanced Transit and Highways (PATH) from 2003, to several additional studies with publication dates ranging from 2010 to 2015. These studies focus primarily on transportation fuel efficiency, with little consideration of impacts on structures. Fitzpatrick et al. noted that a “potential concern regards the increased degradation of infrastructure elements such as bridges would incur due to the closer spacing of trucks. Research is needed to estimate this impact.” Truck platooning with CV technologies places trucks much closer than current design codes anticipate. While this strategy can provide higher fuel efficiency, it also can potentially overload structures. Truck platooning can result in traffic conditions similar to those studied by Barker and Puckett for Wyoming, when interstates are closed due to weather. When the roads are reopened, the delayed traffic rushes onto the road and creates severe congestion. Truck platooning is expected to be deployed imminently, according to the anticipated timeline provided in Trimble et al. The density of truck traffic and the implications for structural safety and serviceability should be considered as part of a platooning policy to avoid compromising bridge service lives. Recent partnering relationships agree with the truck platooning projections by Trimble et al. A broad array of active interested parties was summarized in an online article by Juliussen. Juliussen classified platform users into three categories: logistics fleets (e.g., UPS, FedEx), truck OEMs (e.g., Daimler, Mack), and trucking fleets (e.g., U.S. Xpress, J.B. Hunt). TuSimple, listed among the autonomous vehicle-autonomous truck (AV-AT) software platforms, is particularly noteworthy. On July 1, 2020, TuSimple announced the launch of an Autonomous Freight Network (AFN), “an ecosystem consisting of autonomous trucks, digital mapped routes, strategically placed terminals, and TuSimple Connect, a proprietary autonomous operations monitoring system”. The announcement noted that TuSimple was partnering with UPS, Penske, U.S. Xpress, and McLane. Studies in literature have been limited to strength-based evaluations. Phase I of the proposed research was likewise limited to investigate only the Strength limit state considered in the AASHTO Manual for Bridge Evaluation. The Phase I study found that there were significant opportunities for trucks to carry unusually heavy loads without compromising safety, provided that reductions in live load effect uncertainties and controlled headways and multiple presence scenarios were leveraged.