Vehicles-miles-traveled and Environmental Impacts from On-Demand Delivery: A Systematic Review

The boom of e-commerce and the increasing demand for fast and reliable delivery services has led to the thriving of on-demand delivery (ODD), which provides delivery services to food takeout, grocery, pharmacy, and other light weighted goods. The operational efficiency of ODD is subjected to many factors – access to curbside, delays at the pick-up and drop-off locations, order dispatching mode, vehicle routing schedule, and vehicle refueling needs, among others. The fast-growing delivery orders coupled with operational inefficiencies of ODD will be translated to higher vehicle miles traveled (VMT) and pollutant emissions. Policymakers as well as practitioners need to evaluate the VMT and emissions impact of ODD, given the consumer behavior, operational paradigm, and business models. This paper conducted a systematic review of the existing literature to synthesize and summarize the impacts of ODD with a specific focus on VMT and emissions. The PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analysis) guideline was employed to systematically search for related studies in multiple databases and to crystallize the review scope. The impact evaluation was delved into three aspects: customer shopping behavior (online shopping vs in-store shopping), ODD operational strategy (truck/van vs green vehicles, professional delivery vs crowdsourcing), and business models (home delivery vs depot/collection point). Overall, this study found that online shopping with coordinated ODD can achieve significant VMT and emissions reduction compared with in-store shopping. The reduction extent depends on the customer trip chaining, travel mode choice, residential area type, and the ratio of product return. The use of zero-emission vehicles in ODD, such as electric van/truck/vehicle, cargo-bike, UAV, provides relatively higher emissions benefits; however, those may incur extra VMT due to the charging need and capacity limits. Collection points (e.g., parcel locker, retailer store, postal service point) can reduce VMT and emissions if they are optimally distributed and customers visit them in zero-emission modes or through trip chaining.