Quantifying the Air Quality Impacts of Implementing Access Management

Focus Area

Air Quality


Air Quality






2-3 years

Research Idea Scope

There is a renewed interest nationally and internationally in vehicular emissions, particularly as it relates to the formation of greenhouse gases. To date, there has been no research specific to the air quality impacts of implementing access management treatments. Access management treatments separate speed differentials, remove turning traffic from through lanes, and restrict left turns to improve traffic flow and improve safety. Access management has been shown to be highly effective in terms of improving both traffic safety and traffic flow. Crash rate reductions as high as 50 percent are well-documented in before and after research where access management has been implemented. In addition, improvements in travel speed and traffic flow have also been documented. It is not uncommon for the peak hour mean travel speed of urban arterials to improve by 10 miles per hour after access management treatments have been implemented. While the improved traffic flow implies improved fuel economy and reduced emissions, it has not been quantified. It is well-known that motor vehicles traveling at a near constant speed of 35 to 50 miles per hour tend to produce considerably less pollutant emissions than those involved in “stop and go” traffic. So in theory, access managed roadway facilities should generate air quality improvements.
With rising energy costs and environmental consciousness, especially with regard to ozone and greenhouse gases, there are questions about the amount of air quality and fuel consumption benefits access management treatments provide. Maximum vehicle fuel efficiency and greenhouse gas emissions appear to take place at a speed of 35 to 55 miles per hour. Since access management tends to produce urban arterial roadways that operate at free flow speeds of 35 to 50 miles per hour, there could be demonstrable energy efficiency, air quality, and greenhouse gas emissions benefits from wider implementation of access management treatments.
State environmental agencies and the U.S. Environmental Protection Agency (USEPA) are constantly looking for ways to reduce emissions. In this work, researchers will develop relationships between various access management treatments (or variations thereof) and actual fuel consumption and emissions produced. Collected field data, in conjunction with a fuel consumption and emissions model, will be used to extrapolate the empirical data to develop a methodology to estimate corridor and areawide air quality impacts of access management treatments. This information can also be used for conformity determination. 
The project statement authors are not aware of research directly applicable to this area of study. Air quality studies related to access management treatments were not readily found in the literature. However, numerous studies have been performed using onboard portable emissions testing devices (PEMS) and applying macroscopic and microscopic emissions modeling, which can be applied in conjunction with access management implementation to quantify air quality impacts.
The research objective is to develop and test a methodology to estimate corridor and areawide air quality impacts as a function of access management implementation. 
To satisfy this objective, the following tasks are anticipated:
1.       Perform a literature review of air quality studies and applicable modeling activities;
2.       Develop an experimental design to collect field emissions data from corridors with different access management treatments (or variations thereof), different congestion levels (peak and off-peak), different driving types (hard acceleration/smooth acceleration), and different access density levels;
3.       Develop Interim Report on findings of Tasks 1 and 2, and allow one (1) month for panel review time;
4.       Finalize experimental design based on panel review and collect field data;
5.       Develop corridor and areawide models using the finding from the field data and microscopic emissions models;
6.       Document research results in final report and allow three (3) months for panel review; and
7.       Disseminate the information to the transportation community in the form of a written document and other press releases

Urgency and Payoff

The models developed as part of this research will assist many stakeholders. State environmental agencies and the USEPA are constantly looking for ways to reduce emissions. Transportation engineers and planners can use the research results to better plan and implement access management treatments that are the most environmentally friendly (and under what traffic conditions these occur). The results can be used to persuade local agency decision-makers (elected officials, city managers, etc.) of the air quality benefits of access management. Private shipping companies will find the information valuable as they can use the results to identify roadways with desirable geometric roadway characteristics that can facilitate efficient package delivery and reduce fuel consumption and emissions. For example, UPS uses in-house mapping software to plan trips to avoid making left-hand turns. A UPS press release stated, “In the last year alone, this system has shaved nearly 30 million miles off UPS’s delivery routes, saved 3 million gallons of gas, and reduced emissions by 32,000 metric tons of CO2 ….” The research community, and those promoting access management, will also benefit from quantification of the air quality impacts of access management.
There is urgency in the U.S. to provide low cost solutions to reduce vehicular emissions and the resultant formation of greenhouse gases. The results of this research can be used to determine how effective access management can be in this effort. The payoff potential may be very high, this research is necessary to make this determination.

Suggested By

AHB70, Access Management Committee, as specified in the TRB Research Needs Database, 2009. (Modified in TRB database 12/2008)