Developing a Guide for Estimating Benefits of Closing Gaps in Active Transportation Networks (2026)
Chapter: 4 Summary and Suggested Research
Chapter 4. Summary and Suggested Research
Summary
NCHRP Project 08-149 will result in a best practice guide that outlines how to estimate the benefits of active transportation network gap closures, evaluate who benefits from these gap closure projects, and provide effective approaches to communicate the results. It includes best practices on how to estimate behavior change from improving active transportation networks and then quantify the benefits that accrue for health, safety, emissions, enhanced amenities, and local economic activity.
The guide has been built to allow users with different capacity levels to quickly understand the needed data, assumptions, and limitations as well as final outcomes of each type of benefit estimation. The guide has been designed for use by practitioners, including at state DOTs, as well as regional and local governments. The Basic Methods are intended to be accessible to professionals without specialized skills or resources. The Augmented Methods are analysis methods that provide a more informed analysis using the specific local conditions of the gap. The guide also presents potential methods or examples of benefits estimation that require substantial investment of time and resources and result in sophisticated original analysis. Examples of these Advanced Applications include customized regional travel demand model runs or direct survey efforts to understand the impact of a single project.
Suggested Research
Through the process of developing the guide, the research team identified areas of research need for that would enhance the estimation of benefits from closing gaps in active transportation networks in the future but were not within the scope of NCHRP Project 08-149. Concepts and areas of suggested future research are presented in the list below. The topics presented are not listed in any priority order or ranking.
- The existing research on behavior change is much more developed for conventional bicycling. Research on walk, e-bike, and micromobility behavior-change estimates is sparse, and research on responses to Americans with Disabilities Act accessibility improvements is even more limited.
- There is limited research on how those walking and bicycling may change destinations because of the gap closure. For example, a person who would normally drive to a grocery store several miles away might bike to a closer store after a key gap is closed. Alternatively, someone who normally walks to a coffee shop might walk to a different one that is closer but is now more accessible because of the improvement in a key crossing.
- There are also few reliable studies of reported pedestrian mode substitution — the share of pedestrian trips that would have been made by private motor vehicle. One factor contributing to the lack of research linking infrastructure to pedestrian activity is the limited amount of data on pedestrian activity tied to specific locations. There are some research projects underway that are attempting to address this issue by developing active travel across a network similar to having average annual daily traffic (AADT) estimates for motor vehicles.
- Estimation and allocation of benefits by user type (existing vs. new) have limited research support. Some methods capture only existing or only new user benefits.
- Further research is needed in the area of benefit overlaps between benefit types. Depending on how different benefit categories are captured, care has to be taken in this guide to avoid inadvertently double counting. For instance, when travel benefits are derived from choice models,
- Future research and evolutions of the level of traffic stress (LTS) framework are important areas of ongoing research. For example, there is growing evidence that LTS 1 (least stress) may be too broad of a category that does not work for all user types. Further research in this area is needed.
- Limited research was found regarding temporary conditions, such as snow, ice, and construction activities blocking sidewalks, creating network gaps. These gaps would likely have greater impacts on people with disabilities.
- Further work to allow for regional modeling of active modes, no matter what the capacity of the region, is needed. Regional travel models have only recently started to include the necessary details to estimate cycling and (to a lesser degree) walking impacts; even where they have the capability, model runs are complex and costly.
- In general, more time-series research, studies specific to estimating economic benefits before and after gap closure is needed.
- High-quality crash modification factors for active modes are needed. When considering crash modification factors (CMFs), there are CMFs for some of the most common types of bicycle and pedestrian infrastructure, though not always for all contexts, and the quality of the studies used to develop the CMFs varies. For many countermeasures specific to pedestrian and bicyclist safety, there may not be any high-quality CMFs or any applicable CMFs at all. In addition, NCHRP Research Report 926: Guidance to Improve Pedestrian and Bicyclist Safety at Intersections (Sanders et al. 2020) reviewed evidence on intersection treatments and identified several types of treatments where CMFs were missing.
some portion of health benefits and route safety are likely considered in individual decisions to walk, bicycle or roll, and this portion would need to be subtracted from total social benefits of public health and safety calculated separately. Pending further research, this remains largely a qualitative judgment.
