policy brief
During the COVID-19 pandemic, public transportation systems worldwide faced many challenges, including significant loss of ridership. Public agencies implemented various COVID-19-related policies to reduce transmission, such as reducing service frequency and network coverage of public transportation. Recent studies have examined the effectiveness of these policies but reach different conclusions due to varying assumptions about how passengers may react to service changes.
policy brief
California has a goal of reaching 100% zero emission vehicle (ZEV) sales by 2035. Most ZEV sales to date have been plug-in electric vehicles, with fuel cell electric vehicles (FCEVs) making up only around 1% of ZEV sales. The market for FCEVs may be constrained because, unlike plugin electric vehicles, FCEVs need an entirely new refueling infrastructure network. To date, only 48 hydrogen refueling stations are operational in California. This number will need to increase substantially for FCEVs to become a viable option for consumers. Researchers at the University of California, Davis surveyed more than 700 FCEV drivers about their use of hydrogen fueling stations in California to understand consumer preferences and inform the development of future hydrogen infrastructure.
research report
California has set a goal of reaching 100% zero-emission vehicle (ZEV) sales by 2035. Most ZEV sales to date have been battery electric vehicles (BEVs) or plug-in hybrid electric vehicles (PHEVs), while fuel cell electric vehicles (FCEVs) make up only a small portion of ZEV sales. The market for FCEVs may be partially constrained because, unlike battery electric vehicles and plug-in hybrid electric vehicles, they cannot use any existing infrastructure. This research investigates FCEV driver’s use of hydrogen stations in California (of which there are 47 in operation) with the goal of informing the development of hydrogen infrastructure. Hydrogen station use was studied using results from a 2017 survey of 395 fuel cell electric vehicle (FCEV) owners and a 2018 survey of 328 FCEV owners. The results show FCEV drivers use on average 2.4 hydrogen stations. The average shortest distance FCEV owners would need to travel from home, work, or their commute to a hydrogen refueling station was 10 miles. Those whose most-used station was not the closest station available were more likely than those whose most-used station was the closest to use renewable hydrogen, suggesting that some drivers may prefer renewable hydrogen. Currently, the percentage of California census block groups with one, two, and three hydrogen stations within 10 miles of households are 52.4%, 25.6%, and 22.5%; these census block groups are concentrated primarily in large metropolitan areas. Finally, 70% of FCEV owners said they would not have purchased the vehicle if their primary station had not been available, pointing to the importance of station availability to FCEV adoption.
policy brief
Transportation and other agencies and organizations are increasingly planning and building under- and over-crossing structures to allow wildlife to traverse busy highways. Research has shown that traffic noise and light can impede wildlife species from using these structures. However, existing guidance in the field of wildlife crossing design inadequately addresses how structural and vegetation elements can be used to reduce such disturbance. If wildlife is hesitant to or refuses to approach structures due to noise, light, and other factors, then the structures may have a much lower benefit-to-cost ratio than expected. To help address this gap in guidance for design, a research team led by UC Davis used field measurements and modeling of light and noise from traffic to inform and test wildlife crossing designs. The researchers developed wildlife-responsive designs using berms, barriers, and new paths for two crossings being considered by the California Department of Transportation: 1) the proposed Wallis Annenberg wildlife over-crossing (WAOC) across US 101 in the city of Agoura Hills, and 2) a potential over-crossing across Interstate 15, south of the City of Temecula (TOC). The researchers identified key limitations and opportunities for each design approach and concluded that creating “dark and quiet paths” could increase the wildlife-responsiveness of the designs.
research report
Can congestion pricing be implemented in a way that protects vulnerable residents of California? This report examines that question from two perspectives. First, we empirically estimate the size of the vulnerable population likely to be impacted if congestion pricing were introduced on California’s urban freeways. The research team’s estimates suggest that 13% of households, as a result of their low incomes and current travel habits, might be unduly burdened by a freeway tolling program in California. Second, we consider ways to mitigate these burdens. In particular, we compare freeway use to the use of other metered network infrastructure, like electricity grids or water systems. The research suggests that assistance programs from these utilities provide a useful model for protecting low-income drivers from road prices, and further notes that policymakers would be less constrained in progressively redistributing congestion toll revenue than they would be in redistributing utility revenue.
published journal article
A new technique was used to directly measure O3 response to changes in precursor NOx and volatile organic compound (VOC) concentrations in the atmosphere using three identical Teflon smog chambers equipped with UV lights. One chamber served as the baseline measurement for O3 formation, one chamber added NOx, and one chamber added surrogate VOCs (ethylene, m-xylene, n-hexane). Comparing the O3 formation between chambers over a 3-hour UV cycle provides a direct measurement of O3 sensitivity to precursor concentrations. Measurements made with this system at Sacramento, California, between April–December 2020 revealed that the atmospheric chemical regime followed a seasonal cycle. O3 formation was VOC-limited (NOx-rich) during the early spring, transitioned to NOx-limited during the summer due to increased concentrations of ambient VOCs with high O3 formation potential, and then returned to VOC-limited (NOx-rich) during the fall season as the concentrations of ambient VOCs decreased and NOx increased. This seasonal pattern of O3 sensitivity is consistent with the cycle of biogenic emissions in California. The direct chamber O3 sensitivity measurements matched semi-direct measurements of ratios from the TROPOspheric Monitoring Instrument (TROPOMI) aboard the Sentinel-5 Precursor (Sentinel-5P) satellite. Furthermore, the satellite observations showed that the same seasonal cycle in O3 sensitivity occurred over most of the entire state of California, with only the urban cores of the very large cities remaining VOC-limited across all seasons. The O3-nonattainment days (MDA8 O3>70 ppb) have O3 sensitivity in the NOx-limited regime, suggesting that a NOx emissions control strategy would be most effective at reducing these peak O3 concentrations. In contrast, a large portion of the days with MDA8 O3 concentrations below 55 ppb were in the VOC-limited regime, suggesting that an emissions control strategy focusing on NOx reduction would increase O3 concentrations. This challenging situation suggests that emissions control programs that focus on NOx reductions will immediately lower peak O3 concentrations but slightly increase intermediate O3 concentrations until NOx levels fall far enough to re-enter the NOx-limited regime. The spatial pattern of increasing and decreasing O3 concentrations in response to a NOx emissions control strategy should be carefully mapped in order to fully understand the public health implications.
research report
From March 2020 through March 2021, researchers monitored three San Francisco Bay Area transit agencies: two large – Alameda-Contra Costa Transit District (AC Transit), Valley Transportation Authority (VTA); and one small – Tri Delta Transit. As the lockdown was imposed in response to the COVID-19 pandemic, white-collar commuters, students, and the elderly stopped using public transit. Initially, ridership fell 90 percent, and then over the year slowly climbed to less than 50 percent for AC Transit and VTA, and to around 60 percent for Tri Delta Transit. The pace of recovery was not steady as ridership declined during protests in June 2020, during fare reinstatements in autumn 2020, and during the second COVID-19 wave in winter 2020-21. Agencies’ responses to the pandemic consisted of three parts: 1) maintaining the health and safety of their employees; 2) minimizing the COVID risk for their riders by keeping buses clean and enabling social distancing through capping the number of passengers on buses; and 3) changing their service. There was a direct relationship between the socioeconomic status of the population and transit ridership during the year studied. Higher ridership was observed in low-income areas with a high percentage of Latino, Black, and Asian populations. These are generally renters, who do not have a car, but have to go to work either because they are essential workers and/ or are undocumented immigrants who cannot afford to stay jobless. On the other hand, in wealthy areas of the Bay Area transit activity all but disappeared.
research report
Pilot programs have been implemented in cities across the U.S. to address the first- and last-mile problem with door-to-door shared microtransit, ride-hailing companies, and shared-ride operators with dynamic pick-up locations. The City of Rancho Cordova and Lyft partnered to launch one such pilot in the form of a discount-based door-to-door (D2D) coupon program named “Free ＄5 to Ride”. The program offers ＄5 credits to Lyft riders who start or end their trips at one of four Sacramento Regional Transit District (SacRT) light rail stations. The program was designed to reduce rider dependence on personal vehicles and increase the overall convenience of transit use in the region. UC Davis researchers conducted an evaluation of the “Free ＄5 to Ride” program during its operational period of May 2019 through June 2021. Researchers developed a participant survey and used survey data along with participant trip data, ridership data for the SacRT light rail, and ridership data for the Rancho CordoVan shuttle service to characterize the outcomes of the pilot program. The evaluation shows that the coupon program was generally well-received. Participation levels increased dramatically by early 2020, and while trip activity dropped at the onset of the COVID-19 pandemic, program activity remained fairly constant through the end of the program. Researchers encountered survey sampling limitations due to ride-hailing customer engagement policies, suggesting that future evaluations of similar programs would benefit from increased data access, or modified policies allowing operators to conduct more extensive outreach in support of these studies.
research report
Transportation and other agencies and organizations are increasingly planning and building under and over-crossing structures for wildlife to traverse busy highways. However, if wildlife does not use these structures due to noise, light, and other factors, then the structures may have a low benefit-to-cost ratio. Several criteria are key for their success— sufficient safety and/or conservation need, cost, location, and anticipated use by wildlife. There is limited information in wildlife-crossing guidance on how wildlife biologists should advise designers, engineers, and architects on the use of structural and vegetation elements that could reduce noise and light disturbances. To address this problem, this study used field measurements and modeling of light and noise from traffic to inform and test the designs of two wildlife overcrossings. Wildlife-responsive designs were developed and tested for two crossings being considered or planned by the California Department of Transportation in California. For the planned crossing of US 101 near the city of Agoura Hills (the Wallis-Annenberg crossing), the three designs consisted of noise/glare barriers; noise/glare barriers + berm; and noise/glare barriers + multiple berms. For the potential crossing of Interstate 15 south of Temecula, one design used noise/glare barriers of 3 different heights, and the other had no barriers. Key limitations and opportunities for each design approach were identified. Creating “dark and quiet paths” using a combination of berms and noise/glare barriers could decrease disturbance in the crossing structure approach zones and increase the wildlife responsiveness of the designs.
white paper
Low-carbon biofuels are projected to play a critical role in the early and middle stages of a transition away from petroleum fuels, and they will likely have a longer-term role in uses like aviation and maritime transportation that require energy-dense fuels in high volumes. Policies over the last decade aimed to move low-carbon biofuels squarely into U.S. markets. While these policies encouraged the production of conventional biofuels such as crop-based ethanol, cellulosic fuels that can have a significantly lower carbon footprint per unit of energy failed to materialize at commercial scale.
A research team at the University of California, Davis examined the track record of the past decade for clues as to why this happened and looked forward to 2030 to point to how current policies are likely to still fall short in delivering low-carbon biofuels that can reach scales needed for these hard-to-decarbonize sectors. The findings highlight barriers to low-carbon biofuel development that would safeguard against unintended consequences such as additional emissions from land use changes or higher food prices that can come from competition with the use of crops for fuel. This policy brief summarizes the findings from that research and provides policy implications.
