Transportation and land use planning decisions have numerous environmental and human health consequences.
Many of these impacts are mediated through traffic and its impact on air quality, noise, and pedestrian hazards. The California Environmental Quality Act (CEQA) requires potentially significant impacts of public agency actions to be analyzed and avoided or mitigated, when feasible. A traditional approach to evaluating the traffic impacts of a proposed project is to assess motor vehicle congestion based on average delay per vehicle at select intersections. This method is referred to as Automobile Level of Service or Auto LOS, and grades intersections with little projected delay favorably and those with long projected delays and congestion as having a significant negative impact. Traffic volume/roadway capacity ratios are another congestion-based method that have been used historically.Congestion-based metrics do not account for all traffic impacts on environmental quality and health.
By only using automobile congestion-based metrics to assess traffic impacts, motor vehicle mobility is valued over sustainable transportation modes such as walking and biking. In fact, these measures inform transportation system design that supports swiftly moving cars, a serious hazard for pedestrians with increases speeds increasing the risk of death and injury. Paradoxically, Auto LOS analyses may conclude that pedestrian and bicycle transportation improvements result in motor vehicle delay and thus adverse environmental impacts. Similarly, Auto LOS analysis may create significant regulatory obstacles to smart growth developments including walkable communities and higher density housing. This approach also allows traffic increases to continue until there is congestion, and leads to mitigations that reduce congestion and therefore stimulate driving and its adverse air quality, noise, greenhouse gas emission and pedestrian safety.CEQA thresholds for traffic should be based on environmental and health impacts of auto trips – including air quality, noise, and pedestrian safety impacts.
The United States Environmental Protection Agency has developed or endorsed tools to model the impacts of traffic volume changes on air quality and noise, and health authorities have health-based standards for these environmental attributes. SFDPH’s PHES staff has been using these tools and health evidence in its ongoing work to assess and mitigate adverse air quality and noise impacts from San Francisco land use decisions. Click here for more information regarding our Air Quality Measurement and Modeling and Noise Model research and applications. PHES has also developed a quantitative tool to associate changes in traffic volume and other area characteristics with pedestrian hazards.Local jurisdictions have the responsibility to develop comprehensive and locally relevant indicators and standards for environmental impact assessment under CEQA.
Transportation impact measures informed by the negative impacts of traffic on environmental quality, health and safety would be consistent with other environmental quality measures in CEQA (e.g., noise, air quality), and would not create obstacles to projects that enhance non-motorized transportation use (e.g., the bike plan). Local jurisdictions should also develop and employ measures of bicycle and pedestrian level of service that compliment the consideration of motor vehicle impacts in environmental review. The following timeline details PHES’s work on reforming the CEQA Transportation Impact analysis metrics used in San Francisco.Timeline: PHES work on reforming Auto LOS
In 2003, the San Francisco County Transportation Authority reviewed the use of LOS in a Strategic Analysis Report, making recommendations for improving transportation impacts analysis.
In 2005, SFDPH researched and reported on how the city might replace auto LOS analysis in CEQA with an alternative measure such as vehicle trips in order to support more ecologically sustainable and healthy transportation, consistent with the City’s San Francisco’s Transit First Policy. In April 2005, the Board of Supervisors unanimously approved a resolution declaring auto LOS to be an inappropriate measure of a given project's environmental impact, and requesting that the Planning Commission act to replace Auto LOS with a more meaningful measure, such as vehicle trip generation.
In 2006, the SFCTA began working with a technical group including consultants, City agencies, and advocates to evaluate the justification and feasibility of using a motor vehicle trips measure to evaluate environmental impacts under CEQA. In parallel with these efforts, PHES researchers began developing modeling tools to quantify how changes in vehicles trips impact on environmental noise, air quality, and pedestrian injuries.
In 2007, PHES staff participated in two Transportation Working Group meetings convened by the SFCTA to examine alternatives to Auto LOS, and shared PHES model development and research findings regarding the association of increases in vehicle trips with increases in pedestrian injury collisions in San Francisco. PHES also testified before the Planning Commission regarding Public health perspectives on transportation impacts and implications for CEQA Analysis.
In 2008, SFDPH staff continued to advocate for the Automobile LOS replacement measure and thresholds to be based on the negative impacts of traffic increases on environmental quality, public health and safety. Click here to download a one-page summary of SFPDH’s position, Modernizing Transportation Impacts Analysis Under CEQA.
Relevant PHES Publications
May 2005 working research paper:Replacing auto LOS for Better Health and Environmental Quality: A Public Health Perspective
July 2007 presentation to the Planning Commission:
Public health perspectives on transportation impacts and implications for CEQA Analysis
May 2008 position summary: