Efficiency of Connected Semi-Autonomous Platooning Bus Services in High-Demand Transit Corridors

Abstract

The paper investigates the efficiency of serving high demand transit corridors with connected semi-autonomous bus platoons in both bus and BRT services. Platooning facilitates higher capacity than conventional buses by forming virtual long buses out of multiple smaller vehicles, which may be particularly relevant in scenarios with large demand variations between peak and off-peak hours. The problem is formulated as a constrained optimization problem to minimize total system cost, which includes waiting cost, access cost, riding cost, operating cost and capital cost. For a single period with fixed demand, both analytical solutions and numerical examples are provided. Sensitivity analysis is carried out with regard to demand levels and capacity upper bound. The problem is generalized to a two-period problem considering peak and off-peak demand. Numerical results are provided with sensitivity analysis regarding demand level and ratio of peak/off-peak demand. Furthermore, the impact of a lower bound on service headway is investigated. The result shows that semi-autonomous vehicle platooning is competitive in medium and high-demand scenarios, with the potential of reduced user costs and operating costs at the expense of additional rolling stock costs. Minimum headway constraint, restricted vehicle size, and higher demand ratio all make semi-autonomous platooning more advantageous.