published journal article
conference paper
published journal article
conference paper
published journal article
published journal article
Preprint Journal Article
The Los Angeles County Metropolitan Transportation Authority (LA Metro) started in October 2021 the largest free transit pass program in the U.S. to date. Known as GoPass, it serves students from kindergarten to community colleges in Los Angeles County, the most populated county in the U.S. Although many free transit pass programs have been created, few have been analyzed from the point of view of transit agencies (i.e., for the characteristics of their users and their impact on ridership). To address this gap, the research first examines GoPass’ contribution to LA Metro’s bus boardings, before comparing selected characteristics of the students enrolled in GoPass in 2023 with census data. The research finds some opportunities for additional growth, including for female students. To understand GoPass usage, the research estimated a generalized spatial regression model that explains annual GoPass boardings aggregated by census tract (detailed usage data are unavailable to protect the students’ privacy) using a broad range of socioeconomic and built environment variables. The results confirm the presence of strong spatial effects. The research finds that census tracts with more young males, more transit stops, mixed land use, and more participating schools accessible within 30 min by transit have more GoPass boardings. Conversely, the number of GoPass boardings decreases with more access to private vehicles, property crimes, multifamily units, and a higher population density. A better understanding of the characteristics of GoPass users and GoPass usage is useful to improve GoPass and to inform transit agencies interested in creating similar programs.
published journal article
The primary intent of this paper is to explore the claim that transportation benefits can be derived from neotraditional neighborhood design. Conventional transportation planning models are used as tools to evaluate the performance differences of two hypothetical street networks designed to replicate a neotraditional and a conventional suburban community. Relative transportation benefits are measured in terms of vehicle-miles traveled, average trip lengths, and congestion on links and at intersections. This comparison provides an assessment of how well the two networks in question deal with trips generated by the activities which they serve. All aspects of the modeled communities are held constant except for the actual configuration of the networks. The results of this evaluation indicate that equivalent levels of activity (defined by the land uses within the community) can produce greater congestion with conventional network structures and that corresponding average trip lengths are generally longer. The ultimate goal is to determine if one network type, because of the nature of its design, can result in a more efficient transportation system. The results indicate that neotraditional designs can improve system performance.
published journal article
Efficient operations of traffic signals are of critical importance in urban areas, as signalized intersections prevent the smooth flow of traffic and cause delays. This paper devises an eco-driving algorithm based on connected vehicle technologies, with basic kinematic wave and car-following models. The objectives of the proposed algorithm are to increase the throughput of signal intersections and decrease fuel consumption. Specifically, we focus on a signalized intersection under mixed traffic flows with connected and autonomous vehicles (AVs) and human-driven vehicles (HVs). Through the proposed algorithm, the vehicle speeds at the intersection (i.e., the intersection control speed) and signal timings can be adjusted in response to the real-time traffic conditions. According to the signal timing and the speed at the intersection, the algorithm estimates the time points of each vehicle entering the intersection. An advisory speed limit approach is formulated for each AV, making the vehicle enter the intersection at the allocated timing with the control speed. An onboard alert is set for each HV to stop or pass through. The algorithm is evaluated under various market penetration rates of AVs, different congestion levels, and with signal actuation. The results indicate that the eco-driving algorithm can increase the throughput and average travel speed at signalized intersections in addition to gaining fuel savings.
conference paper
Transit agencies are interested in integrating microtransit service with fixed-route transit (FRT) service to leverage the benefits of each mode. In an integrated FRT and microtransit system, fare structures for both FRT and microtransit services play an important role in influencing travelers’ behavior. This paper studies 10 different fare structures and their impacts on travelers’ behavior in the presence of an integrated FRT and microtransit system. We use a flexible agent-based FRT and microtransit modeling framework recently proposed by the authors to study fare structures. We analyze the impacts of fare structures on synthetic travelers in downtown San Diego and Lemon Grove, a small city in San Diego County. The results show that the intermodal transfer discount policy — where a traveler can use FRT freely when transferring from microtransit to FRT or receives a 50% discount on microtransit when transferring from FRT to microtransit — is the most promising. Under this fare structure, the subsidy per transit rider ($8.20 in downtown San Diego and $13.5 in Lemon Grove), transit user out-of-pocket costs ($1.27 in downtown San Diego and $1.71 in Lemon Grove), and auto mode share (80.6% in downtown San Diego and 86.5% in Lemon Grove) are the lowest of any fare structure.