The State of Connecticut designed an aesthetic guiderail system for use on the Merritt Parkway. Bullard et al. (1996) evaluated this design in accordance to the guidelines specified in NCHRP Report 350 to allow its implementation on the National Highway System (NHS). The Merritt Parkway steel-backed timber guiderail met all National Cooperative Highway Research Program (NCHRP) Report 350 evaluation criteria for test designations 3-11 (LON performance with and without curb), 3-10 (LON performance without curb), and 3-21 (performance of the transition section between the LON of the guiderail and a concrete parapet).  

In all tests performed, the Merritt Parkway steel-backed timber guiderail contained and redirected the vehicle through controlled lateral deflection. The vehicle did not penetrate, or go over or under the installation. In all tests, there were no detached elements or debris from the test article and none of which showed potential for penetrating the occupant compartment or presenting undue hazard to others in the area. The rail performed in all tests in a manner such that serious injury caused by the deformation of the occupant compartment was not probable. The vehicles remained upright and stable during and after collision with the guiderail. In most cases, there was minimal, if any, intrusion into adjacent traffic lanes. The occupant risk factors were within the limits specified in NCHRP Report 350.  

The crash test program conducted in 1996 by Bullard et al. demonstrated that this aesthetic guiderail system complied with guidelines specified in NCHRP Report 350 and was suitable for use by the State of Connecticut on the Merritt Parkway. 

With the adoption of the American Association of State Highway and Transportation Officials/Federal Highway Administration (AASHTO/FHWA) Joint Implementation Agreement on the Manual for Assessing Safety Hardware (MASH) in 2015, specific implementation dates were defined to determine crashworthiness of roadside safety systems to be implemented on projects on the NHS using the 2016 edition of MASH.  The Connecticut Department of Transportation (CTDOT) is very interested in including this guardrail system within its standards as an available roadside safety hardware.  However prior to adding this system to the CTDOT standards, it is necessary to have a MASH compliant system.  CTDOT proposes to full-scale crash test and evaluate the Merritt Parkway Guiderail system performance in accordance to the guidelines specified in the 2016 edition of MASH.   

A testing program was conducted between 2018 and 2021, with the scope to evaluate the Merritt Parkway system through full-scale testing with a 4-inch curb installation under MASH criteria. The system did not pass the evaluation criteria for MASH TL-3.  The system was subsequently modified at the length of need location to reduce post spacing.  The Modified Merritt Parkway Guiderail with 4-inch curb met the performance criteria for MASH TL-3 longitudinal barriers.  In addition, the Merritt Parkway Guiderail Transition met the performance criteria for MASH TL3 transitions. 

The Modified Merritt Parkway Guiderail was also evaluated through full-scale crash testing when installed without the use of a 40inch curb.  The Modified Merritt Parkway Guiderail did not meet the performance criteria for MAS TL-3 longitudinal barriers without installation of the 4-inch curb, due to failure of MASH Test 3-11. 

Benefits

A successfully crash tested Merritt Parkway Guiderail system will be a MASH compliant non-proprietary guiderail that can be used by CTDOT on NHS roadways. 

Products

The TTI research team will generate a report providing the research results on the design, testing, and performance of the MASH 2016 Merritt Parkway Guiderail system.  The research team will provide detailed drawings of the complete system (LON + transition).    

Work Plan

This full-scale crash test will involve a 5,000-lb pickup truck impacting the Merritt Parkway Guiderail LON at 62.2 mph nominal speed and at nominal orientation of 25° (MASH Test 3-11).  The test will be assessed according to the evaluation criteria set in MASH 2016 standards.  The test will investigate vehicle stability, occupant risk and will evaluate the likelihood for the vehicle to experience pocketing or snagging, and undergo excessive occupant compartment deformation.   

Task 5: Full-Scale Crash Test (Test 3-10 on LON, no Curb) 

This full-scale crash test will involve a 2,420-lb passenger car impacting the Merritt Parkway Guiderail LON at 62.2 mph nominal speed and at nominal orientation of 25° (MASH Test 3-10).  The test will be assessed according to the evaluation criteria set in MASH 2016 standards.  The test will investigate vehicle stability, occupant risk and will evaluate the likelihood for the vehicle to experience pocketing or snagging, and undergo excessive occupant compartment deformation.   

Task 6: Full-Scale Crash Test (Test 3-11 on LON, with Curb) 

This full-scale crash test will involve a 5,000-lb pickup truck impacting the Merritt Parkway Guiderail LON, with a curb installed in front of the guiderail. The pickup truck vehicle will impact the system at 62.2 mph nominal speed and at nominal orientation of 25° (MASH Test 3-11).  The test will be assessed according to the evaluation criteria set in MASH 2016 standards.  The test will investigate vehicle stability, occupant risk and will evaluate the likelihood for the vehicle to experience pocketing or snagging, and undergo excessive occupant compartment deformation.   

Task 7: Full-Scale Crash Test (Test 3-10 on LON, with Curb) 

This full-scale crash test will involve a 2,420-lb passenger car impacting the Merritt Parkway Guiderail LON, with a curb installed in front of the guiderail. The passenger car vehicle will impact the system at 62.2 mph nominal speed and at nominal orientation of 25° (MASH Test 3-10).The test will be assessed according to the evaluation criteria set in MASH 2016 standards.  The test will investigate vehicle stability, occupant risk and will evaluate the likelihood for the vehicle to experience pocketing or snagging, and undergo excessive occupant compartment deformation.   

Task 8: Full-Scale Crash Test (Test 3-21 on Transition) 

This full-scale crash test will involve a 5,000-lb pickup truck impacting the transition system connecting the Merritt Parkway Guiderail to the concrete parapet. The pickup truck vehicle will impact the system at 62.2 mph nominal speed and at nominal orientation of 25° (MASH Test 3-21).  The test will be assessed according to the evaluation criteria set in MASH 2016 standards.  The test will investigate vehicle stability, occupant risk and will evaluate the likelihood for the vehicle to experience pocketing or snagging, and undergo excessive occupant compartment deformation.   

Task 9: Full-Scale Crash Test (Test 3-20 on Transition) 

This full-scale crash test will involve a 2,420-lb passenger car impacting the transition system connecting the Merritt Parkway Guiderail to the concrete parapet. The passenger car vehicle will impact the system at 62.2 mph nominal speed and at nominal orientation of 25° (MASH Test 3-20).  The test will be assessed according to the evaluation criteria set in MASH 2016 standards.  The test will investigate vehicle stability, occupant risk and will evaluate the likelihood for the vehicle to experience pocketing or snagging, and undergo excessive occupant compartment deformation.   

Task 10: Report and Recommendations 

The TTI research team will generate a final report of the findings from the research and testing program.  Results will be reported in terms of systems performance, vehicles stability and occupant risk factors and will be compared with respect to MASH 2016 crashworthiness criteria.  The TTI research team will further provide drawings of the railing system and of each of their components. 

If the results of the full-scale crash tests will be deemed successful per MASH 2016, this project is supposed to culminate with a request for FHWA eligibility letter(s) for the tested and evaluated system(s).