Monday, March 24, 2014
Rethinking LOS and transportation impacts of development
For those of us who have worked in the fields of transportation and land use development, the term Level of Service (LOS) is well known and sometimes reviled. It is a measure that is used to calculate delay of motorized traffic at intersections. When new development is proposed, developers often are required to calculate the impact of that development on traffic in the surrounding area, with LOS as the measurement. If the development is projected to generate too much traffic, then either the development must be scaled back or resultant traffic impact must be mitigated, usually through increased road capacity.Problems with using LOS are that the mitigation measures such as wider streets, wider turning radii, dedicated turn lanes, and other measures often make conditions worse for bicyclists and pedestrians. Scaling back development can force new development into less desirable, less dense areas. California is acknowledging these negative impacts and they are rethinking their use of LOS.
At the end of last year, the California Governor's Office of Planning and Research outlined the issues involved in the pdf document Preliminary Evaluation of Alternative Methods of Transportation Analysis, in response to passage of a new law. According to the report, LOS "has recently been criticized for working against modern state goals, such as emissions reduction, development of multimodal transportation networks, infill development, and even optimization of the roadway network for motor vehicles."
The document outlines several problems associated with LOS:
- LOS is difficult and expensive to calculate.
- LOS is biased against “last in” development - infill projects disproportionally trigger LOS thresholds compared to projects in less developed areas.
- LOS scale of analysis is too small - As a result, while outlying development may contribute a greater amount of total vehicle travel and cause widespread but small increases in congestion across the roadway network, it may not trigger LOS thresholds. Further, piecemeal efforts to optimize LOS at individual intersections and roadway segments may not optimize the roadway network as a whole. Focusing on increasing vehicle flow intersection-by-intersection or segment-by-segment frequently results in congested downstream bottlenecks, in some cases even worsening overall network congestion.
- LOS mitigation is itself problematic. Mitigation for LOS impacts typically involves reducing project size or adding motor vehicle capacity. Without affecting project demand, reducing the size of a project simply transfers development, and its associated traffic, elsewhere. When infill projects are reduced in size, development may be pushed to less transportation-efficient locations, which results in greater total travel. Meanwhile, adding motor vehicle capacity may induce additional vehicle travel, which negatively impacts the environment and human health.3 It also negatively impacts other modes of transportation, lengthening pedestrian crossing distances, adding delay and risk to pedestrian travel, displacing bicycle and dedicated transit facilities, and adding delay and risk to those modes of travel.
- LOS mischaracterizes transit, bicycle, and pedestrian improvements as detrimental to transportation. Tradeoffs frequently must be made between automobile convenience and the provision of safe and efficient facilities for users of transit and active modes. Since LOS measures the delay of motor vehicles, any improvement for other modes that might inconvenience motorists is characterized as an impediment to transportation.
- As a measurement of delay, LOS measures motorist convenience, but not a physical impact to the environment. Other portions of an environmental analysis will account for vehicular emissions, noise and safety impacts.
Some measures that have been evaluated include:
Vehicle Miles Traveled: Although VMT counts only motor vehicle trips, not trips taken by other modes, it registers the benefits of transit and active transportation trips insofar as they reduce motor vehicle travel. In this way, VMT captures the environmental benefits of transit and active mode trips. Mitigation to reduce VMT can include designing projects with a mix of uses, building transportation demand management (TDM) features into the project, locating the project in neighborhoods that have transit or active mode transportation opportunities, or contributing to the creation of such opportunities.
Automobile Trips Generated: Mitigation to reduce VMT can include designing projects with a mix of uses, building transportation demand management (TDM) features into the project, locating the project in neighborhoods that have transit or active mode transportation opportunities, or contributing to the creation of such opportunities. Since VMT is sensitive to regional location, it can also be mitigated by choosing a more central location for the project. Used as a transportation metric under CEQA, VMT could encourage reduction of motor vehicle travel, increase transit and active mode transportation, and increase infill development.
Multi-Modal Level of Service (MMLOS) is a metric of user comfort for travelers on various modes. Along with the traditional motor vehicle LOS metric, MMLOS includes additional ratings for transit, walking, and biking modes. However, using MMLOS poses some of the same problems of using LOS.
A final draft of proposed alternates to LOS is planned for July 1, 2014.Automobile Trips Generated: Mitigation to reduce VMT can include designing projects with a mix of uses, building transportation demand management (TDM) features into the project, locating the project in neighborhoods that have transit or active mode transportation opportunities, or contributing to the creation of such opportunities. Since VMT is sensitive to regional location, it can also be mitigated by choosing a more central location for the project. Used as a transportation metric under CEQA, VMT could encourage reduction of motor vehicle travel, increase transit and active mode transportation, and increase infill development.
Multi-Modal Level of Service (MMLOS) is a metric of user comfort for travelers on various modes. Along with the traditional motor vehicle LOS metric, MMLOS includes additional ratings for transit, walking, and biking modes. However, using MMLOS poses some of the same problems of using LOS.
Labels: level of service, LOS, vehicle miles traveled
Thursday, February 2, 2012
Virginia Bicycle Level of Service Maps
VDOT has created a series of maps showing Bicycle Level of Service for major roads in Virginia. The area on the right shows the Dunn Loring/Merrifield area of Fairfax County. It shows the problem we face; there are a few bike-friendly roads (in green) that mostly don't connect. The roads that do connect are level D or E that only experienced cyclists are willing to use.Thanks to TheWashCycle for pointing out these maps.
Labels: level of service, vdot
Wednesday, December 7, 2011
Bike recommendations from I-66 Multimodal Study
At the meeting the various contractors involved in the study displayed panels highlighting different aspects of the study. Toole Design Group is conducting the bicycle and pedestrian portion of the study and they showed maps of the top bicycle recommendations developed so far:
- Lynn Street Improvements
- Scott Street Bridge
- Clarendon Circle
- Fairfax Drive/Kirkwood Intersection
- Fairfax Drive/Custis Trail/Bluemont Junction Trail Transition
- Custis Trail Underpass near Kennebec Street/Bon Air Park
- Bicycle Access to West Falls church Metrorail Station
- Pimmit Hills Connection on Route 7/Leesburg Pike
- Gallows Road Bike Lanes
- Trail Width and Pavement Condition
- Regional Wayfinding
- Trail Lighting
Route 50 at the Beltway is included in the study area. We recommended that bicycle access be provided along Route 50 to connect the residential and commercial areas in Merrifield and Dunn Loring with areas east of the Beltway along Route 50. This stretch of Route 50 is a nightmare for bicyclists and pedestrians due to the character of the road and the number of exit and entrance ramps.
Bicycling and pedestrian access were mentioned numerous times during the presentation. Whether the models being used to assess various "mobility options" will be able to look at other factors besides Level of Service (LOS) for road traffic is another story. Generally the models look at what impact any change in the system has on LOS, which many communities are finding is not a good measure of a livable, bicycle and pedestrian friendly place. LOS is the subject of a recent article entitled The Transportation Planning Rule Every City Should Reform:
"LOS is one of the most widely-used traffic analysis tools in the U.S. and has a profound impact on how street space is allocated in U.S. cities," writes Jason Henderson, geography professor at San Francisco State University, in the November issue of the Journal of Transport Geography.
As Henderson argues, it's about time cities addressed the problem, and San Francisco is doing just that. It's currently in the process of drafting a new sustainable transportation metric that will replace LOS and promote livability. Still, the fight is far from over.
"Every city I've ever come across has some use of [LOS]," says Henderson, who has conducted an extensive review of LOS and is writing a book on the politics of mobility in San Francisco. "LOS and the privilege of the car is the incumbent. The way the political process is set up is you have to disprove the incumbent."
The draft I-66 Multimodal Study results will be published any day now on the project website.
As Henderson argues, it's about time cities addressed the problem, and San Francisco is doing just that. It's currently in the process of drafting a new sustainable transportation metric that will replace LOS and promote livability. Still, the fight is far from over.
"Every city I've ever come across has some use of [LOS]," says Henderson, who has conducted an extensive review of LOS and is writing a book on the politics of mobility in San Francisco. "LOS and the privilege of the car is the incumbent. The way the political process is set up is you have to disprove the incumbent."
We were interviewed by NBC4 reporter Jane Watrel but we haven't seen any coverage of the event yet. We'll post a link here if there is.
Vienna Patch covered the meeting: VDOT Study Could Offer Ideas for Better Travel on I-66
Labels: i-66, level of service, vdot
Friday, January 29, 2010
Tysons Neighborhood Traffic Impact Study
The Neighborhood Traffic Impact Study developed by Fairfax Dept. of Transportation, was conducted to assess the impact of future development in Tysons Corner on neighboring communities. These are the communities where using a bicycle to get into and around Tysons should be a viable option for many short, local trips.As with many "traffic" studies, there is no mention of bicycling and walking. The contractor selected 19 intersections for analysis, using two levels of future density in Tysons and looking at the modeled impact of that development on traffic delay (Level of Service or LOS). Where intersections "fail" with a low LOS, mitigation measures, such as added through or turn lanes, are recommended. The impact of these "improvements" on pedestrian and bicycle levels of service isn't considered.
As Greater Greater Washington explains in The only thing we have to fear is fear of traffic, this narrow view of how the world works isn't very effective when it comes to analyzing how cities work:
The math seems simple. If you build new houses, stores or offices, they will generate a certain number of trips. Roads have set capacities. The added trips will therefore increase congestion and decrease Level of Service (LOS). To avoid congestion, many areas have Adequate Public Facilities ordinances requiring developers to widen the roads.
That's a straightforward formula for adding suburban sprawl. It's the system that built Tysons Corner. But strangely, when a plan comes up for building a real city, people balk. It could never work. It'd generate way too much traffic.
Despite increased growth in the Ballston Corridor, traffic congestion has not increased; people live in mixed-use communities near transit and they walk, bike, and take transit. These factors are often not properly handled with current traffic models.That's a straightforward formula for adding suburban sprawl. It's the system that built Tysons Corner. But strangely, when a plan comes up for building a real city, people balk. It could never work. It'd generate way too much traffic.
See a related post at SF.Streetsblog, Paradise LOSt (Part I): How Long Will the City Keep Us Stuck in Our Cars?.
[It should be noted that despite the above rant on LOS, the conclusion of the Traffic Impact Study was that: "revising the existing Comprehensive Plan by considering the GMU High Land Use Alternative will not cause any significant traffic impacts in the study area."]
Labels: level of service, traffic, Tysons
