Improved Modal Operating Profiles for Fuel Use Comparisons among Modes

Focus Area



Air Quality







Research Idea Scope


There would be value in discerning a realistic auto operating context/profile to use in comparison with transit travel. We tend to compare mean characteristics of the modes when it comes to energy and climate analysis, and yet we know quite a bit about the context for the typical transit trip. In simple terms, this might give us a better profile reflecting temporal and geographic distribution of transit travel in urban areas and identifying the probable auto operating performance in the same context for comparison purposes.


The transit network is less dense and hence more circuitous than the roadway network, depending upon the density and design of the transit network. Thus, a transit trip between a given origin destination is likely to be somewhat longer than the roadway trip. At the same time, an auto trip may involve search for parking spaces or an alternative destination which could add to its emissions. In addition, a transit trip is more likely to occur in a dense urban environment and during peak travel periods when auto performance would be more likely to be compromised by stop and go travel. These differences should be factored into comparisons between modes. There has been little analysis to calculate comparative efficiency measures as a function of such things as roadway or transit network density comparisons and geographic and temporal travel locations. Thus, this analysis would likely lead to some adjustment in the relative model efficiencies and could provide more precise information for specific project or corridor level analyses.


A related element would be to explore the mileage by mode for non-service uses. This is easily determined within transit as deadhead miles for getting vehicles to and from service and for use in training and other purposes. For auto travel there may be value in exploring the availability of data to support estimates of the amount of mileage for supportive actions like trips exclusively for fuel or maintenance or vehicle support functions. 



The objective of this project would be to develop realistic operational profiles of travel by alternative modes between the same origin and destination. Such profiles should take into account indirectness of the trip, access characteristics as well as the actual travel portion of the trip.


Related Work

There are a number of overall energy efficiency estimates by mode and there are some project levels simulation model based findings on vehicle performance, however, the proposers are not aware of any systematic treatment of these issues for use in longer range planning or policy formation contexts. 



The proposed research is timely in order to contribute to the ongoing congressional and federal dialogue on new climate change strategies, policies, and investments.

Urgency and Payoff


The desired project outcome would:

·      Refine an understanding for the comparison of greenhouse gas emissions and energy use of alternative modes for policymakers and members of the public;

·      Define ways to estimate a GHG value for pounds of CO2 per passenger mile traveled, considering local factors. This would contribute to the definition of performance measures and help to rationalize operational investments within the broader context of climate change policy (such as “cap and trade” markets);

·      Review the existing literature on modal profiles to assess its viability in the modeling process for transit GHG impact documentation;

·      Establish a framework for making ‘GHG-smart’ service investments (i.e., routes where buses are full and there is demonstrable additional demand? Provide Bus Rapid Transit (BRT)-like route enhancements to attract discretionary riders to enhance and maximize mode shift?);

·      Detail alternatives for how GHG-related operating assistance could most effectively be provided at the state, metropolitan, or transit agency levels, and establish suggested alternatives for funding sources (and linkages with other climate change programs) as well as performance measures for funding received;

Suggested By

RNS. Sponsoring Committee: A0020T, Special Task Force on Climate Change and Energy Source Info: Special Task Force on Climate Change and Energy January 2010 Workshop