Use of Shared Automated Vehicles for First-Mile Last-Mile Service: Micro-Simulation of Rail-Transit Connections in Austin, Texas

Abstract

Shared fleets of fully automated vehicles (SAVs) coupled with real-time ride-sharing to and from transit stations are of interest to cities and nations in delivering more sustainable transportation systems. By providing first-mile last-mile (FMLM) connections to key transit stations, SAVs can replace walk-to-transit, drive-to-transit, and drive-only trips. Using the SUMO (Simulation of Urban MObility) toolkit, this paper examines mode splits, wait times, and other system features by micro-simulating two fleets of SAVs providing an FMLM ride-sharing service to 10% of central Austin’s trip-makers near five light-rail transit stations. These trips either start or end within two geofenced areas (called automated mobility districts [AMDs]), and travel time and wait time feedbacks affect mode choices. With rail service headways of 15 min, and 15 SAVs serving FMLM connections to and from each AMD, simulations predict that 3.7% of the person-trip-making will shift from driving alone to transit use in a 3 mi × 6 mi central Austin area. During a 3-h morning peak, 30 SAVs serve about 10 person-trips each (to or from the stations), with 3.4 min average wait time for SAVs, and an average vehicle occupancy of 0.74 persons (per SAV mile-traveled), as a result of empty SAV driving between riders. Sensitivity analysis of transit headways (from 5 to 20 min) and fleet sizes (from 5 to 20 vehicles in each AMD) shows an increase in FMLM mode share with more frequent transit service and larger fleet size, but total travel time served as the biggest determinant in trip-makers’ mode share.

SAV Operations on a Bus Line Corridor: Travel Demand, Service Frequency, and Vehicle Size

“…By leveraging the Simulation of Urban Mobility (SUMO) platform that is capable of real-time microsimulation control of passengers and vehicles, SAVs can take ridesharing requests and pick up and drop off passengers through a dispatching pattern. Huang et al [11] further microsimulated a 3 mi × 6 mi central Austin area with SAVs providing first-mile last-mile service to Austin's Red Line commuter rail stations. VMT was predicted to rise 3.7% in central Austin with average vehicle occupancy falling 30% (from 1 to 0.74 people per vehicle), due to empty SAV driving (between riders).…”

“…As seen from existing pilot AV tests, SAVs are anticipated to be implemented commercially in a confined region where full-automation benefits can be realized first, before they can run everywhere. University campuses and central business areas are candidate locations for early SAV implementation [10], and SAVs are also likely to provide first-mile last-mile service near transit stations [11]. is paper investigates another potential service that SAVs can provide, which is replacing the role of 40-seater buses in a traditional transit corridor.…”

Performance Analyses of Information-Based Managed Lane Choice Decisions in a Connected Vehicle Environment

“…The value of travel time (VTT), which is also the willingness to pay to save on one's travel time, is likely to change in a CAV environment. Implementation of CAVs is predicted to move car drivers from human-driven vehicles to autonomous vehicles (AV), assuming that drivers would enjoy the free time in vehicle, reducing their VTTs (3)(4)(5)(6).…”

“…In addition, rather than varying the rerouting percentage, it would be an interesting future work to include the cost of rerouting into the lane choice decision, that is, to change the concept of rerouting from a controlled variable (i.e., a fixed percentage) into a vehicular dependent variable (i.e., one cost of rerouting per vehicle). Recall that, in this study, there are two categories (the income group and the urgency of trip) applied to the entire population (5). Values of travel time distributions (2) were then assigned to those 18 groups (three income groups and six trip situations) based on a mix of traveler survey data and census data from Houston in 2011 (5), assuming 0% CV MPRs at the time.…”

First-Mile-Last-Mile Collector-Distributor System using Shared Autonomous Mobility

“…Although most studies show SAV-FMLM services in a positive light, there is no conclusive evidence that this is true across all regions and transit lines. Huang et al used a microscopic simulator to observe FMLM trips to and from Austin’s Red (light-rail) Line ( 30 ). Their results suggested reduced mode shares for personal cars but significant additions to VMT, and stressed the importance of frequent transit routes and SAV routing strategies to minimize FMLM plus on-board travel times.…”