MASH TL-3 Transition Design with a Storm Drain Inlet (615251/ Task Order DY)

<<Back to Search Results

TTI Research Supervisor:
Akram Abu-Odeh
Texas A&M Transportation Institute
Texas A&M University System
TAMU 3135
College Station, Texas 77843-3135
(979) 317-2682
[email protected]
 Pooled Fund Technical Representative:
Derwood C. Sheppard, Jr., P.E.
Design Standard Engineer
FDOT Roadway Design Office
Florida Department of Transportation
605 Suwannee Street
Tallahassee, FL 32399-0450
(850) 414-4334
[email protected]

Problem Statement

Storm Drain Inlets are meant to be free opening for discharging storm water from roadways as shown in Figure 1.

Figure 1. Example of a Storm Inlet.

However, having such an opening creates a discontinuity for a roadside safety device such as a transition.  Some state DOT’s are considering adopting the guardrail transition developed by the Midwest Roadside Safety Facility (MwRSF) that can be used with or without a 4” (max.) tall curb and gutter configuration.

Figure 2. MwRSF Transition Design with Curb.

However, there is some concerns about a 4” (max.) tall curb being insufficiently tall to contain the flow coming off the bridge on certain structures, and this could result in water flowing over the curb and lead to erosion issues. Thus, there is an interest in guidance on how to address the issue of accommodating inlets capable of handling moderate to high water flow coming off the bridge with a guardrail transition and a curb and gutter.

. The design for such transition would help incorporating storm drain inlet into a crashworthy transition. 


The research objective is to develop a MASH TL-3 Transition Design with a Storm Drain Inlet. The design is envisioned to accommodate storm drain inlet that cannot be addressed via a transition with a curb in front of it. 


The research outcome will provide design to help state agencies use crashworthy transitions while accommodating storm drain inlet. Transition being one of the most challenging devices to perform successfully per MASH. Adding a singularity makes it even more challenging to pass MASH criteria. Hence, a simulation-based approach backed by testing is recommended here to achieve a crashworthy transition that will also address the functional benefit of the storm drain inlet.


TTI researchers will provide a report documenting the simulation cases the results of the crash tests.


The outcome of this project is envisioned to be a feasibility assessment of such unique transition system and a recommendation for completing the testing matrix including upstream and downstream impacts during Phase II. Once all the required tests are deemed passed per MASH evaluation criteria, then the successful system would be ready for implementation by states DOT’s into their standards.

Work Plan

Task 1: Collect and Review Standard of Storm Drain Inlets Designs

TTI will approach the pool fund states and collect and identify storm drain inlets designs. TTI researchers will approach the technical representative of this project and other stakeholders state DOT’s to identify the critical inlet design or design elements to be incorporated into the transition design. 

Task 2: Conduct Simulation

The research team in coordination with the technical representative will define the transition design and start performing finite element simulation to evaluate the performance of the design. The research team will perform iteration on the design to identify performance gaps and opportunity to enhance the system performance. Once a performance is attained through simulation, the research team will recommend the design for testing.

Task 3: Conduct MASH Crash Testing

Upon designing and evaluating the system using simulation, the research team recommends conducting a critical crash test using the pickup truck test vehicle per MASH TL-3 conditions. 

According to MASH, two tests are recommended to evaluate transition.  They are:

  1. MASH test designation 3-20:  An 1100C (2420 lb) passenger car impacting the transition at a nominal impact speed and angle of 62 mi/h and 25 degrees, respectively.  This test is primarily intended to evaluate occupant risk and vehicle trajectory criteria.
  2. MASH test designation 3-21:  A 2270P (5000 lb) pickup truck impacting the transition at nominal impact speed and angle of 62 mi/h and 25 degrees, respectively.  These tests are primarily intended to provide occupant risk, and vehicle trajectory criteria.

However, given the scope and the resources of this proposal, the research team recommends conducting one test to quantity the performance of the design and evaluate the recommended transition system. 

Task 4: Reporting

TTI researchers will summarize the results from Tasks 2 and 3 and prepare a document summarizing the simulation outcomes and tests results.