This document describes part of the work conducted under MOU252 and MOU324, related to the studies of vehicle collisions in vehicle-following operations. This working paper is a detailed documentation of a computer program that is the core element of the simulation tools for vehicle collision dynamics. The program, SMAC (Simulation Model of Automobile Collisions), and its PC-platform version EDSMAC have been used extensively in recent work at PATH to investigate the consequences of vehicle collisions and the effects of vehicle-following parameters on collisions. A copy of the source codes of SMAC was obtained from the University of Michigan Transportation Research Institute (UMTRI). Revisions to the program were made to insert the option of exercising feedback control in collision situations. After these revisions, control algorithms can now be tested in crash scenarios to examine the feasibility and effectiveness of vehicle control in emergency conditions. The structure of the program was outlined in this report with descriptions of the major subroutines. The added options for implementing user-specified steering inputs and feedback controllers were explained in details. An example input file for running the computer program was also provided to illustrate the formats and contents of input parameters. This working report provides a concise and essential documentation for the computer program. KEY WORDS Vehicle Collisions Simulation of Vehicle Crashes Vehicle Control in Collisions Advanced Vehicle Control Systems