FABB Blog

 

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.

To address these concerns, California is in the process of developing alternative transportation criteria and metrics that “promote the reduction of greenhouse gas emissions, the development of multimodal transportation networks, and a diversity of land uses.”

Some measures that have been evaluated include:
A final draft of proposed alternates to LOS is planned for July 1, 2014.

Labels: level of service, LOS, vehicle miles traveled

posted by Bruce Wright at 9:59 PM permalink