Converting existing general-purpose highway lanes to more restrictive access for use only by certain vehicles or travelers has been politically unacceptable ever since the disastrous initial attempt to convert a lane of the Santa Monica Freeway to HOV-only use 40 years ago. Because CV and AV systems can work much more effectively and provide much higher lane capacity when the equipped vehicles are clustered in close proximity to each other in the same lane, these technologies provide new motivations to convert lanes from general use to more specialized uses. The issue of dedicated lanes needs to be restudied now in light of these developments, to develop more authoritative estimates of the benefits that could be gained and of the disadvantages to the general purpose road users who would be excluded from those lanes.
The objective of this research was to develop guidance on the conditions that appear to be amenable to dedicating lanes for CV/AV users and what policy actions are needed to make this feasible. The research describes benefits to CV/AV users in the dedicated lanes and possible dis-benefits to non-users as a function of market penetration .
Task 1. Identified the categories of benefits and dis-benefits that could be experienced by the CV/AV users of dedicated lanes and the rest of the road users who will continue to use the remaining general purpose lanes and that therefore need to be factored into any analysis of impacts. Consider factors such as the following and how they will be distributed across the population of road users:
- Travel time or average travel speed changes
- Traffic impacts of additional lane changes for vehicles transitioning to and from the dedicated lanes
- Traffic flow or speed stability
- Crash risk
- Energy consumption
- Perception of exclusivity or social justice bias (e.g. “Lexus lanes” argument)
Task 2. Evaluated existing modeling frameworks developed for CV/AV applications and define any enhancements that may be needed to estimate the scale of each of the identified benefits and dis-benefits.
Task 3. Identified diverse case study sites that would be useful for estimating benefits and dis-benefits by users and non-users. The analysis included a diverse set of case study sites usable to define guidelines that agencies can use to determine whether their specific applications would merit lane dedication. These case studies evaluated different levels of traffic congestion, network connectivity, availability of alternate routes and modes, spacing of access/egress points, truck traffic, and traffic patterns (core focused versus dispersed).
Task 4. Applied the models to the selected case study sites and assess the benefits and dis-benefits over a range of market penetrations of CV/AV technology to support the determination of which conditions are likely to produce a large enough net benefit to support a decision to dedicate a lane to CV/AV users.
Task 5. Identified the policy actions that need to be taken in support of lane dedication, for the cases in which the benefits appear to exceed the costs.