We have converted the latest FHWA version of SSAM from Java to C++, and added parallel computing capabilities. We also created a user friendly graphical interface to run SSAM. Our fidelity tests have indicated that Java and C++ generate identical safety measures and conflicts. The parallel enhanced C++ version of SSAM is about 90% faster than the original Java version (results may vary).
We also significantly modified the ETFOMM intersection simulation logic. CORSIM/ETFOMM employed gap acceptance models at insertions, but intersection shapes and sizes are not well defined in the model. Vehicles looked at gaps and proceeded through the intersection when gaps were acceptable. Now, vehicle movements are modeled more precisely within intersections. On top of those changes, we have added roundabout and turning way (with/without island) modeling capabilities.
In the coming month, we will first convert the rest of the Java conflict display and statistical analysis functions. We will add more safety measures, such as multiple PET (mPET), multiple TTC (mTTC), and probability of unsuccessful evasive action P(UEA). We will further enhance the SSAM user’s graphic experiences and enhance usability. We propose to add bar chart, Heat Map, Contour Map, Zooming and displaying user defined/selected areas, to display conflict points. Finally, we will add functions to reorganize more safety measures, such as interchange and traffic signal timing related. The latter of which will afford SSAM to help develop signal timing plans, especially in considering yellow and red intervals.
Figure 3 ETFOMM and Other FHWA Software
A Research Project Sponsored by Office of Operations Research and Development
FHWA through US DOT Small Business Innovative Research