Research from UCLA shows that single-rider carpool lane access sells electric vehicles. California leads the way in doling out this perk, and other states should follow in its footsteps, or should I say EV tire tracks.
UCLA’s study evaluated EV sales in four California metropolitan areas, and found that “granting access to 20, 40, and 140 miles of carpool lanes accounted for two, four, and 10 additional sales per census tract, respectively.”
Consider this policy in the context of the timeline of a product’s adoption, more generally known as the Diffusion of Innovations. It is the early stage of product adoption that is often the slowest / most difficult, sort of the birth pains of a product’s entrance into the market and broader world, as reflected in the standard Product Adoption Curve:
Policies that accelerate the Innovators phase of electric vehicle adoption are extremely valuable. The slower the adoption of EVs, the more pollution the global environment endures. Each marginal delay in staving off pollution and climate change yields even greater environmental and socioeconomic damages than those already observed around the world.
At the same time, it would eventually defeat the purpose of the policy to expand HOV (high-occupancy vehicle) lane access too much for too long: with each additional EV-driver who has access to the HOV lane, the less exclusive/valuable this perk becomes. After a certain point, so many people own an EV and can access the HOV lane (as a single driver) that the original perk/incentive and the functional utility of the HOV lane both disintegrate.
This scenario is a long way off, and the main objective as yet is to promote EV adoption, but it still worth considering: eventually policy-makers will want to cap HOV access at some critical mass point along the Product Adoption Curve and gradually expand this cap as sustainable, e.g. in a way proportional to the growth of relevant transportation infrastructure.
This critical mass point is often thought to occur, in most cases, around the 25% market share point:
Given that the market share of plug-in electric vehicles is still, according to many measurements/metrics, well below 10%, it is clearly more important to focus on expansion of EV adoption perks than to worry about when and how to eventually limit them.