policy brief

Vehicle Design May Be Critical to Encourage Ride-pooling in Shared Automated Vehicles

Abstract

In his book entitled Three Revolutions: Steering Shared, Automated and Electric Vehicles to a Better Future, UC Davis Professor Dan Sperling describes two scenarios that could result from new automated vehicles (AVs). In the “nightmare scenario,” consumers privately own AVs and vehicle miles travelled (VMT) per capita increase (along with traffic and emissions) due to greater ease and accessibility of car travel. In the “dream scenario,” consumers relinquish private car ownership in favor of pooling rides in shared autonomous vehicle (SAV) fleets, resulting in a reduction of VMT per capita, traffic, and emissions. Achieving the dream scenario depends on consumers’ willingness to share rides with others. Public policy that incentivizes manu-facturers to produce “pooling-supportive” vehicle design may be critical to encouraging a market shift towards shared mobility. However, little is known regarding the conditions under which riders will tolerate (or even benefit) from ride-pooling. To address this gap in knowledge, UC Davis conducted a study exploring the potential risks and benefits of sharing a ride with a stranger in an SAV, and articulating potential solutions based on vehicle and ride-hailing service design.

research report

Subsidizing Mass Adoption of Electric Vehicles: Quasi-Experimental Evidence from California

Abstract

Little is known about the demand for electric vehicles (EVs) in the mass market. In this paper, the research team exploits a natural experiment that provides variation in large EV subsidies targeted at low- and middle-income households in California. Using transaction-level data, the team estimates two important policy parameters using triple differences: the subsidy elasticity of demand for EVs and the rate of subsidy pass-through. Estimates show that demand for EVs amongst low- and middle-income households is price-elastic and pass-through is complete. THe research paper uses these estimates to calculate the expected subsidy bill required for California to reach its goal of 1.5 million EVs by 2025.

research report

An Examination of the Impact That Electric Vehicle Incentives Have on Consumer Purchase Decisions Over Time

Abstract

The research team investigates the impacts of a combination of incentives on the purchase decisions of electric vehicle (EV) buyers in California from 2010 through 2017. The team employs a comprehensive survey of over 14,000 purchasers of EVs in California. The survey covers a range of purchase intentions, general demographics, and the importance of various incentives. The results indicate that the most important incentives for plug-in electric vehicle (PEV) owners are the federal tax credit, the state rebate, and HOV lane access. In addition, the importance of the incentives and their associated effect on purchase behavior has been changing over time: respondents are more likely to change their decisions and not buy a vehicle at all as time passes and the technology moves away from early adopters.

dissertation, thesis, or capstone

Real Options Models for Better Investment Decisions in Road Infrastructure under Demand Uncertainty

Abstract

Tools used to evaluate transportation infrastructure investments are typically deterministic and rely on present value calculations, even though it is well-known this approach is likely to result in sub-optimal decisions in the presence of uncertainty, which is pervasive in transportation infrastructure decisions. This dissertation proposes a framework based on real options and advanced numerical methods to make better road infrastructure decisions in the presence of demand uncertainty. A real options framework was developed to find the optimal investment timing, endogenous toll rate, and road capacity of a private inter-city highway under demand uncertainty. Traffic congestion is represented by a BPR function, competition with an existing road is captured by user equilibrium, and travel demand between the two cities follows a geometric Brownian motion with a reflecting upper barrier. The result shows the importance of modeling congestion and an upper demand barrier –features missing from previous studies. The real options framework was extended to study two additional ways of funding an inter-city highway project: with public funds or via a Public-Private Partnership (PPP). Using the Monte Carlo simulation, the value of a non-compete clause was investigated for both local government and private firms involved in public-private partnerships. Since road infrastructure investments are rarely made in isolation, the real options framework was extended to the multi-period Continuous Network Design Problem (CNDP) to analyze the investment timing and capacity of multiple links under demand uncertainty. No algorithm is currently available to solve the multi-period CNDP under uncertainty in a reasonable time. A new algorithm called “Approximate Least Square Monte Carlo simulation” is proposed and tested that dramatically reduces the computing time to solve the CNDP while generating accurate solutions.

presentation

Asphalt Pavement Maintenance & Rehabilitation

policy brief

Electric Assisted Bikes (e-bikes) Show Promise in Getting People Out of Cars

Abstract

For over a decade, California has offered incentives towards the purchase of zero-emission vehicles as part of the state’s broader effort to reduce greenhouse gas emissions. Expanding California’s incentive program for zero-emission vehicles to include electric assisted bikes (e-bikes) has been a point of recent discussion. The following summarizes the existing evidence on the effects e-bicycling has on car travel, characteristics of e-bike incentive programs, and opportunities for increasing e-bicycling in California.

policy brief

Mobility Challenges Facing Older Adults: A Contra Costa County Case Study

Publication Date

April 1, 2019

Author(s)

David Ragland, Sarah Doggett, Tracy McMillan

Abstract

Meeting the mobility needs of an aging population is one of the most substantial challenges facing California in the coming decades. The number of residents age 60 and above will grow to 13.9 million by 2050, representing over 25% of the state’s population. Meanwhile, the number of residents age 85 and above is expected to increase by over 70% between 2010 and 2030. Many older adults, who have primarily been auto dependent, will reduce or stop driving due to medical and non-medical reasons. Declines in age-related physical functions may also reduce the ability to walk to access goods and services, and can make using public transportation more difficult. These reductions in mobility can have a negative impact on the physical and mental health of seniors.

research report

Evaluating the Impacts of Start-Up and Clearance Behaviors in a Signalized Network: A Network Fundamental Diagram Approach

Abstract

Numerical simulations have shown that the network fundamental diagram (NFD) of a signalized network is significantly affected by the green ratio. An analytical approximation of the NFD has been derived from the link transmission model. However, the consistency between these approaches has not been established, and the impacts of other factors are still unrevealed. This research evaluates the impacts of start-up and clearance behaviors in a signalized network from a network fundamental diagram approach. Microscopic simulations based on Newell’s car-following model are used for testing the bounded acceleration (start-up) and aggressiveness (clearance) effects on the shape of the NFD in a signalized ring road. This new approach is shown to be consistent with theoretical results from the link transmission model when the acceleration is unbounded and vehicles have the most aggressive clearance behaviors. This consistency validates both approaches, but the link transmission model cannot be easily extended to incorporate more realistic start-up or clearance behaviors. With the new approach, this project demonstrates that both bounded acceleration and different aggressiveness lead to distinct network capacities and fundamental diagrams. In particular, they lead to start-up and clearance lost times of several seconds; and these lost times are additive. Therefore, the important role that these behaviors play in the NFD shape is studied to reach a better understanding of how the NFD responds to changes. This will help with designing better start-up and clearance behaviors for connected and autonomous vehicles.

research report

Assessing and Addressing the Mobility Needs of an Aging Population

Publication Date

April 1, 2019

Author(s)

David Ragland, Grace Felschundneff, Kara MacLeod, Sarah Doggett, Tracy McMillan

Abstract

The mobility needs of an aging population is one of the most substantial challenges facing California in the coming decades. The number of residents aged 65 and older is expected to double between 2012 and 2050, and the number aged 85 and above is expected to increase by over 70% between 2010 and 2030. Declines in physical function related to age may reduce mobility options dramatically. A survey of 510 residents aged 55 and older in Contra Costa County was conducted to determine mobility patterns and limitations related to age and other factors. Results of the survey indicate that a majority of seniors are car-dependent. However, some older adults miss important activities due to mobility limitations associated with increasing age, poorer health, living alone, not having a licensed driver in the household, and having a disability. Mobility options are also limited in some geographic areas and demographic groups. Importantly, older adults want to “age in place.” Based on these findings and those in related studies, the travel options and the quality of life for older adults, now and in the future, can be greatly enhanced if efforts are made to develop mobility solutions beyond the use of private vehicles. The findings support the recommendations of recent regional plans such as the Coordinated Public Transit–Human Services Transportation Plan (2018), adopted by the Metropolitan Transportation Commission (MTC) of the San Francisco Bay Area, which recommends supporting a range of mobility options centered around shared mobility and accessibility for populations at risk for limited mobility.