Measuring twice, cutting once: Integrating sustainability into transportation planning

Tailoring and transportation share at least one thing in common — the better the planning, the better the product.

When tailors measure cloth twice before cutting, they’re maximizing efficiency and minimizing waste by first calculating carefully. In the transportation planning arena, that’s what sustainability is all about.

“Sustainable transportation” means different things to different people. In its recent project for the Texas Department of Transportation (TxDOT), the Texas Transportation Institute (TTI) defined it as “the provision of safe, effective and efficient access and mobility into the future while considering economic, social and environmental needs.” These needs are often called the “three pillars” of sustainability.

By measuring and applying these principles, a more sustainable — or safer, more effective — transportation system can be established. It’s easy enough to dream of sustainability, but without specific performance measures, it’s much more difficult to quantify and implement its principles.

“The three pillars are tied together by many cross-cutting issues, including how they affect and are affected by the development of our transportation system,” explains Joe Zietsman, director of TTI’s Center for Air Quality Studies. “What we’ve done is to figure out how we can measure these pillars of sustainability using data that’s already available.”

Zietsman’s team used TxDOT’s own strategic goals as a framework for defining how the pillars interact. With these goals in mind, the team developed sustainability objectives, created 13 sustainable transportation performance measures and a methodology for benchmarking them, and derived a method for combining those measures in one index for comparative purposes. This whole process was coded into a user-friendly Microsoft Excel®-based calculator.

Since the performance measures and their underlying methodology are uniform, researchers can compare different corridors and different sections of the same corridor in terms of their relative sustainability. A comparison can also be made over time between baseline and future conditions. This output can then be used by TxDOT to enhance the relative sustainability of their transportation corridor projects while ensuring the efficacy of their strategic goals.

“The 13 measures can help TxDOT see a more realistic portrait of the transportation system by simultaneously considering all three dimensions of sustainable transportation,” says Zietsman.

Researchers refined the methodology by evaluating case studies involving transportation corridors in San Antonio, Houston and Amarillo. That field work proved the flexibility and effectiveness of TTI’s approach in rural, urban and suburban environments.

Bill Knowles, TxDOT’s project coordinator, notes, “TTI’s research on this project provided a valuable planning method that is both practical and easy to use. The project findings are now being rolled out as an implementation project through a series of workshops in Texas’ largest metropolitan areas.”

As the United States looks to improve its transportation infrastructure, proactive planning tools like these will prove vital to getting the most from its transportation dollar.

SUSTAINABILITY: A concept, not a technology

“Sustainability” is an idea comprising multiple goals that need to be related to one another and quantified. Unlike an innovative technology — like a new kind of crash barrier on the roadside — it’s a concept, not a piece of equipment. And sometimes that makes it difficult to understand.

Through this project, TTI researchers made the abstract more concrete by identifying objectives and performance measures organized around TxDOT’s five goals: reducing congestion, enhancing safety, expanding economic opportunity, increasing the value of transportation assets and improving air quality.

Using their spreadsheet in a case study in San Antonio, the TTI team projected that the overall sustainability of the corridor got worse over time despite proposed capacity enhancements. In this example, the calculator gave TxDOT specific information about why sustainability actually got worse along the corridor. It also helped them understand how their strategic goals were affected by those results and where the problem occurred along the corridor.

“Using data that’s readily accessible, our analysis tool gave us important information on how TxDOT can improve the sustainability of the test corridors,rdquo; says Zietsman. “Using the calculator, TxDOT can proactively identify remedies that will actually make a difference before ever beginning a project.”

map showing US-281 test section

Location of study corridor for US-281 Case Study. It stretches from IH-410 in downtown San Antonio in the south to the Comal/Bexar county line in the north.

photo of US-281 test section

Study section of US-281 near downtown San Antonio.

Traffic Volumes for Base Case and Future Case Scenarios: US-281
Link Length (miles) Daily Volume (2005) Number of lanes (2005) Daily Volume (2025) Number of lanes (2025)
1 3.89 101,364 6 156,129 6
2 5.22 77,314 6 169,629 6
3 3.97 36,884 4 102,067 6
4 1.85 33,887 4 75,261 6

This Issue

Improving our Infrastructure

The Highway 6 flyover in College Station is expected to relieve the congested and dangerous intersection that existed in the above photo.

Volume 45, Number 1
March 2009
Issue Overview

“TTI’s research on this project provided a valuable planning method that is both practical and easy to use. The project findings are now being rolled out as an implementation project through a series of workshops in Texas’ largest metropolitan areas.
Bill Knowles,
TxDOT project coordinator

For more information:

Joe Zietsman
(979) 458-3476
zietsman@tamu.edu
or
Tara Ramani
(979) 845-9888
t-ramani@ttimail.tamu.edu