# Measurement of Regional Electric Vehicle Adoption Using Multiagent Deep Reinforcement Learning
## 1 Introduction
Generally, each $1000 subsidy has a 12-15% effect [17]. Other subsidy types, such as industrial subsidies [16] or subsidies for deploying chargers, also improve EV sales [18]. However, recent studies have begun to challenge the general assumption regarding subsidy benefits for EV consumers [13; 19]. For instance, [PERSON] et al. [19] recently argued that current policies structurally fail to achieve emission savings because disadvantaged households often undertake long-distance vehicle travel and are not adequately'rewarded' by economic savings.  
Currently, most states in the U.S. favor a uniform distribution of subsidies. However, a few have initiated tiered subsidy programs to offer price buy-down opportunities to low-income communities. For instance, California's Clean Vehicle Assistance (CVA) program provides up to $7500 in subsidies alongside affordable financing opportunities with interest rates below 8% [20]. A city like Riverside offers rebates ranging from $1000 to $2500 for used BEVs or Plug-in Hybrid Electric Vehicles (PHEVs) purchased or leased after 1 January 2023 [21]. The necessity to financially assist disadvantaged communities is evident, given California accounts for 40% of U.S. state EV sales [22]. However, consumers with low or moderate incomes make up only 0.6% of new PHEVs and BEV buyers and 1.8% of new hybrid electric vehicle (HEV) buyers [22]. It remains uncertain how different levels of financing would affect EV adoption among low or moderate-income households, even after conducting policy simulations [22]. While the upfront financial benefits of EV ownership are apparent [23] and the adoption of tiered incentive programs is being discussed, it is still unclear how to establish the appropriate parameters. This research presents a framework based on a reinforcement learning approach to simulate a regional EV adoption scenario. The primary goal is to gauge the impacts of offering additional incentives to low-income communities. Low-income residents often live further from their workplaces and have longer commutes [24]. Transitioning them to driving EVs makes achieving the targeted net zero emission goals easier. The importance of addressing their reluctance to adopt EVs should be recognized. Our study incorporates the peer effect among consumers [24; 25] and the interaction effect of climate change on EV purchasing decisions [26], using multiagent systems that represent high- and low-income groups. Our case study focused on Austin, Texas (TX), where a uniform subsidy distribution is implemented. Like many U.S. cities, Austin has experienced significant racial divisionsstemming from interstate highway programs in the 1950s and 60s. Despite these challenges, as of 9 May 2023, Austin boasts the highest percentage of registered EVs in TX, at 1.95% of total registered vehicles [27]. The City of Austin (COA) has set the ambitious goal of replacing 40% of all vehicles in Austin with electric counterparts by 2030, and it has been actively promoting this transition [28]. Additionally, Tesla's engineering headquarters is located in Austin. Beyond the focal state leading the EV adoption, another case study that illustrates the early stages of EV adoption can help us devise a better transportation electrification plan. The insights from Austin's experience could be applicable and beneficial to other cities. Hence, EV equity studies show a possible bias towards the West Coast, as observed by [PERSON] et al. [29], who reviewed seven North American literature pieces on this subject. Five of these studies were focused on the West Coast, including California, Seattle, and Los Angeles, while only two originated from the East, specifically Chicago and NYC. States like Florida and Texas, which follow California as leaders in EV adoption in North America [30], are overlooked. Furthermore, the equity literature rarely includes studies that 'explicitly' mention equity or justice with normative frameworks [31]. Among 37 peer-reviewed articles in mainstream journals, a mere 29.7% directly address equity in EVs.