Integrating spatial safety data into transportation planning processes [R15]

Travel demand models enable us to forecast the state of the transportation system under different scenarios such as changes to demand, transportation infrastructure and policies. By using a wide array of performance measures, planners can evaluate scenarios and compare their performance including but not limited to regarding cost, mobility, and emission with base scenario. Despite previous attempts to integrate road safety into planning models, one area that needs further attention is the safety of road users (instead of road entities) and how changes in travel patterns due to changes in transportation infrastructure and demographics affect the safety of road users. To compare the safety performance of scenarios, we developed an HBA Safety Performance Function (HSPF). Similar to the traditional SPF that estimates the expected safety of a road entity, HSPF estimates the expected safety of road users in a particular traffic analysis zone (TAZ) based on their average trip frequency, trip length and modal splits. The main report focuses on developing the HSPF and evaluation of two scenarios based on the Nashville Metropolitan area travel demand model. Findings indicated that HSPF could be used to evaluate and quantify the safety impact of travel demand alternatives and it is strongly correlated with the travel characteristics of the road users at the TAZ level. To illustrate how HBA can be integrated into travel demand models as well as other relevant sources of data, we present four case applications. Each application illustrates different applications of the HBA to explore factors affecting road safety.