For over 50 years, Level of Service (LOS), the predominant method of measuring traffic generated by new developments, has done more harm than good.
To mitigate traffic, LOS has often required developers to widen streets and augment intersections to move cars more efficiently – at least in the short term. But in the long term, LOS brings more and more traffic.
“If you just add capacity in hopes of maintaining LOS, you end up in a vicious cycle where you induce more demand, you squeeze out other modes, and you end up with more cars and more congestion,” Eric Sundquist, Director of the State Smart Transportation Initiative (SSTI), told me.
This is one reason why, despite policies meant to encourage alternatives to cars, traffic in cities has actually increased faster than population. From 1990 to 2015, the metropolitan population has gone up some 30 percent while urban interstate lane miles have increased 68 percent, according to a new report, and accompanying webinar, from SSTI and the Mayors Innovation Project.
The costs of such autocentric development are manifold, according to the SSTI report, and encompass the high price of owning and operating individual vehicles, travel time lost in congestion, traffic accidents, parking space, road construction, the taking of valuable land, traffic services, air pollution, climate change emissions, noise, costs of petroleum and other resources, impacts on nonmotorized vehicles, land use impacts, water pollution, and vehicle disposal.
Fortunately, a new means of measuring traffic is on the rise, one that uses vehicle miles traveled (VMT) as its primary metric. When developers pay to mitigate VMT, the result is more public transit, more walkability, and better bike lanes and facilities. Getting fewer cars to drive fewer miles does wonders for a community.
What exactly is Level of Service?
LOS, that dinosaur of a tool, involves counting the number of vehicles that pass through a given signalized intersection in a given period of time, then assigning that intersection a grade of A through F. If the rating is too low, a new developer is required to pay for improvements; however, this has usually meant increasing space for more cars. LOS thus places “expensive burdens on desirable new land uses,” induces traffic, harms the environment, degrades safety and livability for residents, and encourages car use, according to the SSTI report.
LOS also divides development into parcels, rather than looking at overall impacts. Any addition to traffic has impacts up and down the line, but LOS does not account for these. As the SSTI report puts it, “Cities adopted parcel-level mitigations not because they were shown to work, but because other ways to address congestion were politically or fiscally unfeasible.” Political considerations plus inertia have kept a bad system for decades.
In contrast to LOS, VMT, when used as a measurement of how much mitigation is needed, encourages travel modes other than automobile. Modern mitigation based on VMT “seeks to reduce auto traffic through demand reduction rather than to induce it through supply increases,” explains the SSTI report. It encourages both fewer and shorter car trips and prompts thriving, multi-modal districts in place of highway-oriented ghost-towns.
As with so many issues related to the environmental, California is leading the way, in 2013 passing SB 743, which requires a change from LOS to VMT. Sundquist described the law as “the best-kept secret, really,” the most “important new statute out there.” He hopes it sets a standard across the country. Yet implementation is only beginning statewide, notably with a 2015 initiative in Pasadena, CA, and in San Jose and San Francisco.
From measurement to mitigation
Calculating VMT is just the first step. Once developers assess a new project, they are required to mitigate. As the SSTI report explains, “Mitigation . . . is the practice of requiring contributions— in dollars or in-kind—from developers in order to address transportation impacts anticipated from a new or changed land use.” If LOS is the tool used, it’s also possible that one developer may bear the burden of traffic generated by several previous projects, as traffic reaches a failing level. VMT, by contrast, looks at the whole system.
Ramses Madou, the Division Manager of Planning, Policy, and Sustainability for the Department of Transportation in the City of San Jose, in the webinar, discussed his city’s mitigation when a project increases VMT, dividing it into four major areas. The first is the project level, where density and design can be constructed to encourage walkability, biking, and transit.
Infrastructure, the second factor, can include, for instance, pedestrian and bike networks and traffic calming. It’s crucial to think about convenience for bikes and peds, not just for drivers; for instance, bicycle parking needs to be located where it’s most convenient (not behind a dumpster, as has been known to happen). Furthermore, providing affordable housing can greatly reduce driving; studies show that low-income residents use public transit more often when given the opportunity.
Parking supply, Madou’s third area, should be limited, not mandated as has long happened. It’s best if parking is unbundled, that is paid for as it’s used, and not by those who don’t drive as currently happens. Finally, Madou discussed transportation demand management, including ride-sharing, telecommuting, and transit access, as an extremely successful tool for reducing solo driving, one that’s been in use since the 1970s.
To help projects efficiently work in these four areas, San Jose provides an implementation tool, downloadable here. San Francisco has implemented a similar system that requires developers to select mitigation strategies from a number of options, based largely on parking spaces, as discussed previously in Mobility Lab.
Switching to what works
The misuse of LOS has created a true tragedy-of-the-commons situation, in which all of us pay the costs whether we benefit or not. And many of these costs are hidden—once an individual has bought a car, and society has paid for a road network and other infrastructure, it’s all too easy to just jump in and go, blissfully unaware of the multiple problems one is adding to.
These problems remain, and even grow, in spite of laudatory efforts on the part of cities and local government. Overall, said Sundquist, policy announces such objectives as increasing walkability and reducing greenhouse gas emissions, but these too rarely occur on the ground. The right regulation is needed to effectively implement policy. With LOS as the primary measurement mechanism, policy and regulation have often been at cross purposes, with grand vision statements encouraging greener cities while roads are widened on the ground.
That could change quickly. If VMT becomes a more standard tool of regulation, following California’s lead, expect to see greener, more walkable, people-friendly cities with less traffic.
Photo of people using Santa Monica’s walk and bike path from Flickr’s Creative Commons.