what is happening between the loop detectors that still need some resolution. This is a fascinating area for statistical research.

Terry Klein noted that a useful way to begin developing indicators would be to identify the specific objectives of producing the indicators. For example, should the indicator appeal to the public in an effort to change their attitudes and behaviors toward transportation issues? Or is it simply a tool for policy makers and decision makers to be kept apprised of the state of transportation? The indicators would be very different depending on which objective is used. If the objective is to target the media, the indicator would have to be fairly simple to understand.

Klein also mentioned that he liked the idea of a market basket of trips, but that there is a data collection problem in trying to ascertain trip type, in both the numerator and the denominator. Survey data would help collect some of the denominator data, and over time those data can be gathered. But in the numerator, for example, it can be difficult to figure out the purpose of the trip if it was involved in a fatal crash and only one person was in the car.

He then suggested that BTS should defer work on some of the economic growth indicators because it seems as if there are others who are working on the issue. The objective of the economic growth indicators is unclear. Is it to show the effect of transportation on stimulating economic growth or how economic growth affects transportation? Both? Neither? He observed that since a consensus cannot be reached on what the existing data actually mean, BTS should not start working on economic indicators right away.

Nathaniel Schenker stated that the Consumer Price Index and the unemployment rate are good models to follow in developing transportation indicators. They are well-established indicators, and both of these measures are broken down into many different measures, such as unemployment by age, race, region, and so on.

Douglas Robertson reiterated the importance of clearly defining an audience before beginning to develop transportation indicators. There is more than a single audience for this type of information, so it is important to group the audiences according to some criteria. And it is important that the audiences not only understand the data that they are provided with, but also that they act on those data. Consequently, newly developed indicators must have a purpose that is based on a need for the information that they provide. Many of the indicators discussed today did not have a clearly stated purpose. Consequently, Robertson would not spend any money on



The National Academies | 500 Fifth St. N.W. | Washington, D.C. 20001
Copyright © National Academy of Sciences. All rights reserved.
Terms of Use and Privacy Statement