Traffic counts, traffic mixes and site geometry combine to influence the probability of a collision and the magnitude of the consequences of a collision and are not included in the Specification. A probabilistic risk analysis for determining the design requirements should be considered/developed for designing piers and abutments for vehicle collisions. Magnitude of the design force (400 KIP) was established from data available at the time the LRFD Specification was prepared. Additional data/information are now available and more are needed to address whether the magnitude of the 400 KIP design force should be changed. Recent tests with single unit trucks colliding with fixed bollards and concrete walls have yielded data that will be applicable. More information for heavily loaded articulated vehicles is still needed. Some helpful information might be obtained from reconstruction of recent collisions of such vehicles that have occurred in the field.

The AASHTO LRFD Bridge Design Specifications require that "abutments and piers located within a distance of 30.0 FT of the edge of the roadway, or within a distance of 50.0 FT to the centerline of a railway track, shall be designed for an equivalent static force of 400 KIP..." Supporting documentation for this design requirement, both its applicability and the magnitude of the design force, is not extensive. Further detailed guidance for the design engineer is not available. Two issues need to be addressed: 1. What risks warrant application of this requirement? 2. Is the magnitude of design force (400 KIP) appropriate?

This project will be conducted in two phases, as listed below. All Phase 1 work shall be completed, and recommendations for Phase 2 work (if any) approved by the project sponsors, prior to commencement of any Phase 2 research activities. Project Phasing and Suggested Tasks: Phase 1 (18 months, $300,000 estimated) will include the following tasks: 1a. Literature review, 1b. Computer simulations of vehicle/bridge column and abutment collisions, 1c. Accident survey and analysis study, 1d. Development of a risk analysis methodology for vehicle/bridge column and abutment collisions (analogous to AASHTO LRFD vessel impact requirements). 1e. Detailed justification and work plan for research (if any) to be conducted under Phase 2 of the project. 1f. Provide facilities and host a meeting to present Phase 1 results to project sponsors, including pooled fund project participants from other state DOTs. Include $20,000 line item in project budget for reimbursement of travel expenses for out-of-state participants. Phase 2 (6 months, $125,000 estimated) may include the following tasks: 2a. Crash testing with a single unit truck to verify loading from Phase 1 literature survey and computer simulations. 2b. Crash testing of a 5-axle tractor trailer rig to verify loading from Phase 1 literature survey and computer simulations.