BACKGROUND 

Derailment loads in nearly all U.S. transit design criteria documents are similar to each other. Various agencies modified the loads between 1985 and 2005 with no documented or defined basis. Currently, vertical impact is defined as 100% acting on any truck in the train, while horizontal derailment load is taken as 40% of a single carload acting on one truck. Lateral excursion in both cases is taken as a maximum of 3 ft, which assumes that a vehicle will not travel further after derailment. Neither of these loads have been experimentally verified and appears to be based on an arbitrary definition that has become the norm in the U.S. industry. It is unknown whether this load is reasonably accurate, overly conservative, or too liberal. 

Research is needed to formulate a rational load within acceptable limits of accuracy to ensure the efficient and safe design of bridges. The transit vehicle industry has the tools to simulate the entire vehicle derailment and use these models to check the safety of the vehicles. The industry can leverage their expertise and knowledge and extend their models to determine the loads on the bridge in the vertical and lateral directions.

OBJECTIVE

The objective of this research is to determine accurate horizontal and vertical derailment loads for the efficient and safe design of transit structures. 

At a minimum, proposers shall address the following to achieve the research objective: 

• Select a representative vehicle or vehicles using a rational method.
• Analyze typical track configurations (e.g., ballast, direct fixation, etc.).
• Utilize numerical modeling to determine the horizontal and vertical impacts. This might be supplemented by physical testing with a test plan and expected outcomes that are clearly defined. 
• Validate the derailment loading model that assumes loads on a single truck.
• Establish derailment load criteria that complement the American Association of State Highway and Transportation Officials (AASHTO) LRFD Guide Specifications for Bridges Carrying Light Rail Transit Loads.
• Establish extreme event (derailment) load factors and combination.

RESEARCH PLAN

The research plan shall be divided into tasks that present, in detail, the work proposed in each task. The research plan shall describe appropriate deliverables that include, but are not limited to, the following (which also represent key project milestones):

• An Amplified Research Plan that responds to comments provided by the project panel at the contractor selection meeting;
• An interim report (i.e., a technical memorandum or report) and panel meeting or videoconference that occurs after the expenditure of no more than 40% of the project budget;
• A draft final comprehensive research-based report;
• A final comprehensive research-based report; and
• A technical memorandum, titled “Implementation of Research Findings and Products”.

STATUS: A research agency has been selected for the project. Research in progress.