Increasing motor vehicle usage and traffic congestion is a growing concern in many urban and rural areas. Environmental degradation, petroleum-based fuel usage and its resulting contribution to rising carbon dioxide levels, hours spent sitting in traffic, and the lack of reliability in the time it takes to travel from place to place are only a few of the problems caused by traffic congestion which lead to a lowered quality of life.
Congestion pricing is one of the congestion mitigation solutions that is starting to be used across the globe to help alleviate these problems. A variety of different approaches to congestion pricing exist. Each approach has different strengths and weaknesses. High Occupancy Toll (HOT) lanes are designed to improve the efficiency of roadways, given the inability to supply roadway capacity to all of the people who would like to use it during peak periods. When congestion is present, HOT lanes help allocate the available roadway space, by providing travelers with a price/performance choice that allows each user to select for each trip they make whether to select a lower cost, but slower and less reliable travel path, or a more expensive, but faster and more reliable path.
Relatively little work has been done exploring how this approach to pricing is actually used. Do only high-income households pay for faster, more reliable trips? Do low-income households use it, and if so, how often, and at what price? From a policy perspective, public decision makers wish to understand the equity aspects of HOT lanes. Users of the HOT lanes pay more than non-users, but they gain travel benefits from those payments. Are the benefits of these lanes equitably distributed or not?
It is important for any transportation agency operating a HOT lane to understand the uses and benefits obtained from these systems, as well as their impacts on different groups. Monitoring the use and performance of these systems over time is also necessary to understand when changes in system operations need to occur to ensure a more equitable outcome.
The Washington State Department of Transportation (WSDOT) implemented a HOT facility along the I-405 corridor in the Puget Sound (Seattle) region in 2015, following the implementation of one other HOT lane (SR 167) in the region, and other facilities in San Diego, Houston, Minneapolis and elsewhere. As policies like congestion pricing and HOT lanes are more frequently implemented by cities around the world, empirical analysis is critically important. WSDOT has a vested interest in the gap of quantitative analysis that currently exists in the literature regarding how HOT facility use varies across user characteristics such as income, race and commuting patterns.
Using data from I-405 HOT lane users for all of 2018, this report aims to provide quantitative information about how the lanes are being used, how the costs and benefits of the lanes are distributed, and how changes in facility operations could affect these distributions.
We specifically want to answer the following questions:
How are the I-405 HOT lane facility’s benefits and costs distributed among and within different groups of users?
Are there any inequitable distributions that could be better addressed or made known to WSDOT?
What policy implications or recommendations can we make to address potential inequities?
When evaluating whether HOT lanes are equitable, many researchers point out that in addition to evaluating absolute equity, relative equity must also be considered via comparison against alternative methods of reducing congestion such as roadway-network expansion. Most researchers also note that whether HOT lanes are progressive or regressive (where progressiveness is taken as a proxy for equitability) really depends on how revenue generated is spent. For the purposes of our study, however, we focus explicitly and solely on understanding the equitability of direct HOT lane use, access, costs, and benefits, while acknowledging that this is a far from complete picture of overall HOT lane equitability.
We define equity in two ways:
Benefits of the HOT lane facility that we will analyze include:
We will look within and across groups defined by:
WSDOT is responsible for managing traffic across the state, and in particular operating the I-405 HOT lane facility. As WSDOT manages the dynamic pricing system, reinvests toll revenues in corridor improvements, and can make policy recommendations about the toll lanes, the agency’s decisions have major effects on commuters. Consequently, WSDOT is very interested in the equity impacts of the facility—how the costs and benefits of HOT lanes are distributed among and within different groups. WSDOT is the primary stakeholder for our analysis.
But our analysis, through its effects on WSDOT’s decision-making, has the potential to impact drivers on I-405, both in and out of the HOT lanes. These drivers may be classified into four main categories:
Drivers may also be classified by income group, or geographic area. Our analysis must carefully consider the effects on each of these groups, and ensure that the concept of HOT-lane equity we develop is not too narrow.
The primary ethical issue at stake in this project is that of privacy. The tolling system records each driver’s license plate, and, where present, the RFID tag, which together allow drivers to be linked to an accounts database containing sensitive information such as names, home address, and vehicle models. This personal information, along with the time and location information associated with each toll transaction, could, in the wrong hands, allow drivers’ movements to be tracked with a concerning level of precision. WSDOT, aware of the major privacy risks associated with these data, provided us with records where all personally identifiable information had either been removed (home address, names, vehicle information) or obfuscated (account number, RFID tag number, license plate) by means of a cryptographic hash function. Yet de-identifying records may not be enough when time and location data are provided. For an additional layer of security, the database containing the tolling records was securely encrypted and decrypted for each use. Unencrypted data containing potentially identifying information was never stored on disk or transmitted over the internet.