Development of an Innovative Tool to Help Regional Air Quality Districts Model On-Road Emissions

Output of Spatial Emissions Estimator model that uses color coding to show Houston area onroad vehicle nitrous oxides emissions by links, zone, and hour on a GIS map of the area

Project Brief

The Challenge

A city’s air quality managers must ensure that their transportation plans will help the city meet federal air quality standards that protect human health and the environment. Estimating the emissions from an urban area’s transportation network of roadways, truck stops, and parking areas is no simple task: the transportation models, as well as the inventory of vehicles, emission controls, fuels, and operating characteristics, are varied and complex.

ERG's Solution

In response to this challenge, ERG helped develop a computer model to calculate on-road emissions at a high spatial resolution and allow a streamlined approach between producing detailed inventories for regional air quality modeling and producing aggregate numbers for transportation conformity analysis. 

This computer model, named the Spatial Emissions Estimator model, calculates emissions from vehicles using EPA’s vehicle emissions model MOVES and Houston’s travel demand model used for long-range transportation planning. ERG used the SEE model in the Houston-Galveston-Brazoria area to calculate emissions at the link level within eight counties and also improve spatial resolution for emissions from vehicles parked away from roads. SEE also makes it possible to include emissions from the Port of Houston and other heavy-duty truck emission “hot spots” in Houston’s regional air quality planning.

To make SEE user-friendly, ERG developed a Python-based graphical user interface with a supporting Perl and MySQL backend, which prepares MOVES input files and databases using hourly link data from Houston’s travel demand model.

With the success of this project, ERG is now using the SEE model in other regions of Texas and beyond.


Houston-Galveston Area Council