As more U.S. cities eliminate parking minimums and encourage infill housing development, competition for residential curb space is likely to become more common. This report examines the impacts of unmanaged curb parking in high-demand neighborhoods, the range of residential parking permit (RPP) programs cities have developed in response to these impacts, and the outcomes, distributional effects, and welfare implications of different policy approaches. The report also considers the political economy of residential curb management and the opportunity costs of dedicating public space to parking. Research findings suggest that demand-based pricing for permits and visitor parking can help encourage more efficient use of existing off-street parking, improve curb availability, and generate revenue that can be reinvested in transportation initiatives to support a transition to a less car-dependent future.
To improve the safety of automated vehicles, this study developed a mathematical model to indicate the degree to which certain traffic conditions, driver characteristics, and behaviors of an automated driving system (ADS) affect the probability of a driver safely taking over control in a level 3 ADS to avoid a potential crash. (A level 3 ADS requires the driver to intervene when the ADS cannot safely handle a situation.) Experiments in which 50 participants used a driving simulator informed the model development. The presence of a warning signal from the ADS telling the driver to intervene significantly reduced collision probability, improved driver reaction time, and increased the safety margin between the study vehicle and the vehicle in front of it. Traffic complexity—the number of nearby vehicles—increased the probability of hard-braking, tailgating, and steering variability, and it increased the drivers’ perceived workload and distrust of automation. The absence of a driver warning from the ADS interacted with higher traffic complexity, so that their combination greatly increased collision probability. These findings indicate that driver warnings provide measurablesafety benefits and will be used to refine the model and examine the effects of the design and timing of warnings.
This research presents a risk-informed framework to derive metrics characterizing and tracking the safety performance of heavy-duty automated vehicles (HD-AVs) operations. A combination of traditional and novel hazard identification methods are leveraged to study potential human-system interactions in HD-AVs operations, ranging from safety drivers to remote operators.
This report synthesizes research on the impacts of parking infrastructure, the effects of minimum parking requirements, and the outcomes in cities that have repealed them. Parking infrastructure has negative impacts on urban design, environmental sustainability, and walkability, while increasing car ownership and driving. Minimum parking requirements contribute to parking oversupply and constrain new development. Research finds that eliminating minimums not only slows the expansion of new parking but also encourages adaptive reuse, supports more housing development in areas where minimums are removed, and expands housing options by enabling smaller units. Ultimately, the evidence indicates that repealing mandates facilitates more affordable, sustainable, and economically vibrant cities.
Across the United States, zoning codes require new developments to provide a minimum number of parking spaces, which carry substantial construction costs. In this report, we use 2025 construction cost estimates from Rider Levett Bucknall to calculate the cost per space in 17 U.S. cities and combine these data with local minimum parking requirements to estimate how parking mandates increase total construction costs across building types. We find that parking construction costs have risen substantially faster than inflation since 2012 and that required parking can account for a large share of total project costs—adding tens of thousands of dollars per housing unit and, in some cases, increasing total construction costs by more than 50%. These findings can help inform evaluations of the economic and development impacts of maintaining minimum parking requirements.
This report analyzes the optimal organization of public transit service in large U.S. metropolitan areas—like Los Angeles and the San Francisco Bay Area—where multiple operators serve overlapping markets. We synthesize over 50 international and U.S. studies of: (1) regional transit governance and coordination, (2) economies of scale and scope in transit operations, and (3) service contracting. We find that regions gain the most from coordinating front-end, customer-facing functions such as marketing, fares, information, and service planning through a regional association or authority, while leaving back-end service-production and delivery decentralized among sub-regional operators. This approach enhances riders’ travel experience, increases ridership, and improves cost efficiency. Conversely, large-scale transit agency mergers rarely save money and often introduce diseconomies of scale due to increased organizational complexity and higher labor costs. For some large agencies, contracting certain services coupled with strong oversight and performance-based incentives can lower costs. We conclude that combining regional coordination of front-end, customer-facing functions with decentralized back-end service production offers an optimal blend of service coordination and costeffectiveness.
This report develops a transportation hydrogen roadmap for California projected to 2045, building on previous UC ITS work, in part for the ARCHES hydrogen hub for trucks and ports. This study adds modes such as airports, aircraft, rail systems, and fuel-cell light-duty vehicles. Based on a scenario of high adoption of hydrogen-fueled transport, these modes and sectors would use 1000 tonnes/day of hydrogen by 2035 and 5000 tonnes/day by 2045. To 2035, about 40% of the expected growth occurs in heavy-duty trucking. Another 20% is used by other truck types, about 20% by light-duty vehicles, and 20% by other modes, notably shipping and aviation. These shares remain similar to 2045. Trucking remains the dominant driver of demand. Shipping, aviation, and rail are not anticipated to account for an increasing share of demand in the scenarios in this study. This hydrogen fuel system would support around 6,000 jobs per year. Hydrogen vehicle adoption will depend on strong policy support, coordination of planning and investments, and rapid scale up to reach a hydrogen system that can be self-sustaining, on the order of hundreds of tonnes per day by 2040.
A growing number of U.S. transit agencies are adding transit ambassadors to their systems to improve the customer service and safety experience for passengers. These personnel can play a variety of different roles, including providing wayfinding, system navigation, fare payment support, and other passenger support roles that enhance the customer experience. This research examines the Los Angeles Metro’s transit ambassador program, which began as a pilot in 2022 and is moving in-house in 2025 as a permanent program. Ambassadors provide key customer service functions that are not filled elsewhere. Ambassadors spend most of their time with vital, basic tasks of orienting and aiding riders; they also assist with the first level of homelessness response, with crisis de-escalation, and by administering Narcan to prevent overdoses. Broadly, they provide more eyes on the system and offer a highly visible presence to riders. Training during the pilot period was customer-service oriented but lacked thorough instruction in conflict resolution techniques. The contractor model, while quick to implement and iterate, created some employment drawbacks during the pilot phase, such as paying below living wages, lack of on-the-job resources, and reports of strenuous working conditions. System satisfaction, ratings, and safety perceptions increased over the period ambassadors were deployed, but we lack data to draw firm causal conclusions. The program to date demonstrates progress towards meeting the intention to advance a community safety approach to meeting riders’ needs and appears to be making a positive contribution to the system.
What changes to policies and procedures at the California Department of Transportation (Caltrans) would increase transfers of agency-owned excess land to California Native American Tribes and groups negatively impacted by freeway development? Using case studies on LandBack and reparations and qualitative research with Caltrans staff and community advisory groups, the research team developed recommendations for Caltrans’ excess land process, community performance measures, an overview of relevant policies, and examples of land return around the state.
This study identifies equity challenges in current transportation payment systems, specifically for transit, parking,and vehicle tolls. The methodology included comprehensive literature reviews, an inventory of 49 global transitsystems, seven case studies, and expert interviews to assess payment accessibility, technical rules,interoperability, and user privacy.The study found that current systems disproportionately burden low-income, unbanked, and disabled usersthrough high complexity and lack of cash-equivalent options. To mitigate this, the report recommends designingand deploying a California Mobility Card (CMC). The CMC would be a reloadable, prepaid transportation cardoperating on an existing, widespread payment network, offering cash-equivalent anonymity, seamless crosssystemtravel, and automatic access to discounts like fare capping.
