research report
A vulnerability assessment of California roadways to post-wildfire debris flows is developed. The work examines current and future conditions, considering climate change scenarios and how they affect fire risk and precipitation. Results show how post-fire debris flow risks change from today into the future. A discussion is presented on how to prioritize investments considering the criticality of roadways within the broader network.
dissertation, thesis, or capstone
research report
Drivers know that smartphones distract them. Trying to limit distraction, drivers can use hands-free devices, where they only briefly glance at the smartphone. However, the cognitive cost of switching tasks from driving to communicating back to driving adds an underappreciated, potentially long period to the total distraction time. This project measured the effect of hands-free smartphones on driving behaviors by engaging ninety-seven 21- to 78-year-old individuals who self-identified as active drivers and smartphone users in a simulated driving scenario that included smartphone distractions. Peripheral cue and car-following tasks were used to assess driving behavior, along with synchronized eye-tracking. This research found that simulated driving performance drops to dangerous levels after smartphone distraction for all ages and for both voice and texting. The participants swerved for 15.1 seconds after a voice distraction and for a longer 20.6 seconds after a text distraction. Participants from the 71+ age group missed seeing about 50% of peripheral cues within 4 seconds of the distraction. Coherence with the lead car during the following task dropped from 0.54 to 0.045 during the distraction, and seven participants rear-ended the lead car.
dissertation, thesis, or capstone
published journal article
If we expand roadway capacity, more drivers will come, or so economic theory suggests and a substantial body of empirical research now shows. Despite strong evidence, the “induced travel” effect is often ignored, underestimated, or misestimated in the planning process, particularly in the assessment of the environmental impacts of roadway capacity expansions. Underestimating induced travel will generally lead to an overestimation of the traffic congestion relief benefits a highway expansion project might generate, along with an underestimation of its environmental impacts. A major reason that induced travel tends to be underplayed in environmental analyses is that travel demand models do not typically include all of the feedback loops necessary to accurately predict the induced travel effect. We developed an online tool, based on elasticities reported in the literature, to facilitate the estimation of the induced vehicle travel impacts of roadway capacity expansion projects in California, with potential future expansion to other geographies. We describe the tool, apply it to five case study highway capacity expansion projects, and then compare the results with the induced travel estimates reported in the environmental impact analyses for those projects. Our results suggest that environmental analyses frequently fail to fully capture the induced vehicle travel effects of highway capacity expansion projects.
presentation
conference paper
Electrification of transportation network companies (TNCs), such as Uber and Lyft, presents possible paths to increased social benefits from reduced vehicle emissions and enhanced implementation of renewable electricity as well as private benefits to drivers via reduced vehicle fuel and maintenance costs compared to conventional vehicles. We conducted a survey of plug-in vehicle (PEV) drivers on the Uber platform in the US. This paper describes these drivers and their experiences driving PEVs on TNCs to further our understanding of barriers to PEV adoption among TNC drivers and identify strategies to promote further adoption.
published journal article published journal article presentation
presentation presentation presentation research report
Investigating the dynamics behind the likelihood of vehicle crashes has been a focal research point in the transportation safety field for many years. However, the abundance of data in today’s world generates opportunities for a deeper comprehension of the various parameters affecting crash frequency. This study incorporates data from many different sources including geocoded police-reported crash data, curbside infrastructure data, and socio-demographic data for the city of San Francisco, CA. Findings revealed that the GFMNB model provides a better statistical fit than the FMNB and NB models in terms of AIC and log-likelihood, while the NB model outperformed both mixture models in terms of BIC due to the model complexity of the latter. Among the significant variables, TNC pick-ups/dropoffs and duration of parked vehicles were positively associated with segment-level crashes.
conference paper
Vehicles that travel on a multi-lane highway issue data packets that are to be disseminated over a targeted geographical span. A roadside infrastructure consists of Roadside Units (RSU) that are connected by point-to-point links. We develop RSU-aided and V2V-based millimeter wave (mmWave) packet dissemination algorithms. We develop FDMA/TDMA-based spatial reuse scheduling schemes for sharing communications links in the system. System parameters include inter-RSU and inter-vehicular distance ranges, transmit power levels, antenna beamwidth values, and spatial reuse factors. We study the delay throughput performance behavior of the system. We characterize the magnitude of attainable performance enhancement as the density of the RSU infrastructure is increased. Also, we show that under an RSU density that is higher than a demonstrated level, and under strict message delay requirements, critical messages will experience much lower delays under the RSU-aided scheme. When lower-priority non-critical data flows are involved, we note the two algorithms yield similar throughput capacity levels.
published journal article published journal article 
