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.
Since 2009, pedestrian fatalities have risen by 80%, which mirrors the increase in the average weight of vehicles accompanying the rising popularity of SUVs and pickup trucks. Additionally, many modern safety and environmental technologies, including those in electric vehicles, contribute to increased vehicle weight. Heavier vehicles generate greater kinetic energy, which can lead to a higher risk of fatalities and serious injuries in crashes. This research synthesis examines the relationship between vehicle weight, design, and safety for road users, particularly pedestrians. However, not all studies find a statistically significant link between vehicle weight and pedestrian injuries, possibly because even lighter vehicles already weigh so much more than pedestrians. Existing research indicates that vehicle design is a more critical factor. For example, the higher front ends of light trucks are more likely to strike a pedestrian's upper body and abdomen, causing more severe injuries than the lower front ends of sedans, which typically impact the legs. Our findings suggest that design changes, such as lowering front-end heights and adding safety features, would be more effective in reducing risks to pedestrians from vehicle crashes.
The Carbon Reduction Program (CRP) requires transportation projects to demonstrate measurable reductions in transportation-related greenhouse gas (GHG) emissions, but the impact of priced managed lanes and related roadway pricing projects on emissions can vary. Thus, there is a need for a transparent framework that can place evidence within a common statewide emissions metric. This report develops a screening framework to translate project-level GHG impact data from CRP-relevant projects in California into a wider statewide framework for emissions accounting. The preliminary framework separates the direct effects of a priced managed lane project on roadway travel demand from its indirect effects. In a case study analysis, the I-580 managed project lane is predicted to directly increase VMT and CO2 emissions through induced travel demand. However, reinvestment of the lane’s revenue in regional transit is projected to reduce VMT and CO2e emissions. In conclusion, a CRP GHG accounting should evaluate direct roadway effects and reinvestment effects separately before integrating them within a common statewide emissions accounting framework.
This report presents a data collection plan for evaluating the greenhouse gas (GHG) impacts of high-occupancy toll (HOT) lane projects implemented under Caltrans' Carbon Reduction Strategy. Because HOT lanes can affect route choice, departure time, vehicle occupancy, and destination choice beyond the managed lane corridor, the report recommends evaluating impacts across the regional travel shed. We recommend two approaches for reliable before-and-after estimates of vehicle miles traveled (VMT) by speed bin. The household-based survey approach uses OBD-II, GPS, or smartphone-based tools to observe a representative sample of households within the travel shed, yielding the most detailed evidence on regional VMT and how impacts vary across the population. The infrastructure-based approach combines continuous freeway sensor data with sampled counts and speeds on arterials, local roads, and ramps; it is less costly and easier to implement but offers less insight into the travelers behind observed changes. For each approach, the report describes what data to collect, where and when to collect it, and how to validate and integrate it with EMFAC. The report also includes order-of-magnitude cost estimates for the two alternatives.
A rapid transition to a near-zero-emission transportation system in California and Europe will require rapid uptake of transportation technologies, changes in transportation services, and investments in associated infrastructure. These in turn require policy innovations. This report compares California and EU policies across three broad areas: 1) greenhouse gas (GHG) targets for 2030 to 2050; 2) progress on reducing GHG emissions from different transportation modes; and 3) current strategies and policies to achieve targets. Differences by region and across major modes are identified. Strategies cover electrification, uptake of hydrogen, aviation and shipping fuels, and modal shifts. Policies include regulatory requirements (fuel economy and CO2 standards, fuel standards); incentive programs, including taxation, feebates, and others; direct investment programs; equity considerations and environmental justice-related initiatives. In both geographies, a range of impactful policies are in place. However, these fall short of guaranteeing that targets will be met, and more actions will likely be needed. Some possibilities are presented, with a particular focus on pricing strategies.
In the San Francisco Bay Area, earthquake damage to a small number of critical transportation facilities can produce regionwide mobility impacts. This report evaluates the Berkeley Hills Tunnel, a key Bay Area Rapid Transit (BART) cross-hills connection, using an integrated model that links tunnel seismic performance to transportation consequences during disruption and recovery. The model couples scenario-based seismic assessment of the tunnel with screening-level fragility for substitute corridors and propagates the resulting time-dependent capacity states through a transportation simulation. At a representative recovery-stage demand of 25 percent of normal, mean cross-hills travel time rises from about 9 minutes in the mildest scenario (327-year return period) to about 41 minutes in the most severe (654-year). In that severe case, a fully subscribed bus bridge can lower the mean cross-hills travel time by up to 30 percent. Uncertainty quantification identifies recovery-stage demand as the dominant source of travel-time variance and shows that unfavorable capacity combinations can nearly double travel time relative to the central estimate. Disruption falls disproportionately on transit-dependent travelers, who either endure longer travel times or pay an extra travel fee. Agencies can use the workflow to assess disruption impacts and identify likely bottlenecks, compare recovery-stage operational strategies, and target equitable service for affected populations.
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.
Airports play a critical role in emergency response and disaster recovery, yet are highly vulnerable to earthquakes. Past earthquakes in California, including the 1989 Loma Prieta, 1994 Northridge, and 2014 South Napa events, caused infrastructure damage, power outages, and operational delays at airports, affecting both safety and mobility. As seismic risk remains high across the state, improving airport resilience is critical to maintaining transportation access and supporting emergency operations.Earthquake Early Warning (EEW) systems offer a way to reduce these risks by providing seconds to tens of seconds of advance notice before strong shaking begins. While this technology has been around for several decades across the world, the development of the ShakeAlert system has brought it to the West Coast recently, giving airports in the region the chance to be early adopters of the technology in the United States. To better understand how EEW could be used in airport settings, we examined its operational applications, benefits, and implementation challenges across different types of airports.
Cargo e-bikes are emerging as a promising solution for sustainable urban freight delivery, offering advantages over conventional van-based systems in emissions reduction, congestion mitigation, and operational flexibility. This white paper examines the current state of cargo e-bike deployment in the United States, identifies key barriers to adoption, and provides evidence-based recommendations for policymakers and urban planners. Despite a rapidly growing global market—with projected annual growth of 11–15% through 2034—cargo e-bike deployment faces three interconnected challenges: infrastructure gaps (microhub locations, bicycle network coverage, and parking); regulatory inconsistenciesacross jurisdictions regarding vehicle specifications and permitted infrastructure use; and operational challenges including higher upfront costs and battery-related concerns. To overcome these barriers, this report recommends that cities establish microhub networks, expand bicycle infrastructure, ensure adequate parking with charging capabilities,develop consistent regulatory frameworks, and implement financial incentives and pilot programs. Coordinated action across these domains can enable cargo e-bikes to realize their potential as transformative elements of sustainable urban logistics.
This research evaluates LA Metro's GoPass program—a fare-free transit initiative for K-12 and community college students—through asurvey of Los Angeles Community College District (LACCD) students. We investigated students' travel preferences through a discretechoice experiment, assessed GoPass awareness and participation impacts on transit use, and analyzed spatial and seasonal ridership patterns from TAP card records. GoPass participation increased transit use by 26 percentage points for school trips and 19 percentage points for discretionary trips, with greater benefits for socioeconomically disadvantaged students. Even students aware of GoPass but not participating showed a 5.8 percentage point increase in school-related transit use. However, 39% of eligible students were unaware of the program, and car access reduced transit use probability by 37 percentage points. The discrete choice experiment revealed students valued travel time savings at $27–$54 per hour and Wi-Fi availability at $6–$7 per trip. Modest travel time reductions generated larger welfaregains than free fares alone, suggesting service improvements may offer better returns than fare subsidies. Analysis of 1.1 million TAP cardrecords showed substantial seasonal variation: summer ridership declined 37.5% for buses and 32.2% for rail. Single-vehicle householdsmaintained more consistent usage (+11.9%), while three-vehicle households showed the largest declines (-40.9%). Areas with high transit stop density and high violent crime maintained more consistent usage, reflecting transit-dependent populations. These findingsdemonstrate that increasing student transit ridership requires addressing service quality, coverage, and program awareness beyond farereductions alone.
