Presentation on theme: "M.A.S.H.: The New Safety Hardware Crash Testing Criteria"— Presentation transcript:
1M.A.S.H.: The New Safety Hardware Crash Testing Criteria Idaho Transportation Department2011 Project Development ConferenceM.A.S.H.: The New Safety Hardware Crash Testing CriteriaRichard AlbinFederal Highway AdministrationResource Center Safety and Design TeamApril, 2011
2Crash Testing - History Crash Testing has been used as a tool for evaluating the safety performance of roadside features for many years.
3History of Testing Procedures Procedures for how to perform crash tests have evolvedHighway Research Correlation Services Circular 482 (1962)NCHRP Report 153 (1974)NCHRP Report 230 (1980)NCHRP Report 350 (1993)
4NCHRP 350 NCHRP Report 350, was formally adopted by FHWA for the NHS This was the first time that FHWA adopted these proceduresAn implementation date was established in 1998 for new installations on the NHS.
5Practical Worse Case Philosophy Developing testing criteria that represents all of the conditions that may be encountered on the highway system is very challenging. It would be impractical to test safety features with every vehicle make and at every speed and impact angle that might be encountered. In addition, when you consider roadside conditions such as side slope that affect the placement, there is an infinite number of possible impact conditions.The crash test criteria is based on a philosophy of Practical Worst Case to reduce the number of tests to a couple of tests that that can be conducted economically and for conditions where it is reasonable to expect hardware will be able to successfully pass the test.The test vehicles were selected as surrogates that represent the majority of passenger vehicles on the highway.The Speed and angle individually represent the 85 percentile, meaning that for run off the road crashes, 85 % are expected to impact a feature at less than the highest speed of 62 mph and 85 % are expected the leave the roadway at a departure angle of less than 25 degrees. When you combine these, it is expected that less than 5 % of run off road crashes exceed both the 62 mph speed and the 25 degree angle.With the Worst practical case philosophy, it is understood that there may be conditions were hardware performs differently then tested. A crash tested device does not guarantee 100% positive performance.
7Test Matrix NCHRP Report 350 created 6 Test Levels Levels 1-3 based on speedTL1 – 50 km/h (31 mph)TL2 – 70 km/h (43 mph)TL3 – 100 km/h (62 mph)Levels 4-6 add large trucksNCHRP Report 350 also introduced the concept of test levels. Six test levels were identified. The first 3 were based on speed and specified impact speeds of 50, 70, and 100 km/h ( which is approximately 31, 43 and 62 mph). Test level 3 was intended as the basic test level for high speed facilities and used the 100km/h impact speed. Test level 3 used two vehicles (highlight 1st box) a 820kg or 1800 lb car and the 2000 kg or 4400lb pickup truck.An optional test using a 700kg car was also identified however very limited testing was ever conducted with this vehicle. For test level 1,2,3 (highlight 3rd box) the specified impact angle for the small car was 20 degrees and the angle for the pickup truck was 25 degrees. Test Levels 4, 5, and 6 added tests with larger vehicles. The impact speed for these tests were 80km/h or 50 mph and the impact angle was 15 degrees. For videos of the different test levels click on the links on the left.
8Manual for Assessing Safety Hardware (MASH) Update of the evaluation procedures preparedPublished as AASHTO document in October, 2009Implementation plan also developedIn 2009, NCHRP report 350 was 16 years old and there had have been many changes in the vehicle fleet as well as advances in hardware since the report was first published. To reflect these changes, an update was prepared. However to address concerns from the states regarding the implementation of NCHRP Report 350, the process for developing the new criteria was changed significantly.One change was testing with the proposed new criteria was conducted prior to adoption.It was also decided that the criteria would be published as an AASHTO document. The AASHTO document containing the crash test criteria was published in late 2009 and is called the Manual for Assessing Safety Hardware or MASH.Prior to publishing, AASHTO worked with FHWA to develop an implementation plan.
9Manual for Assessing Safety Hardware (MASH) Primary Focus of UpdateUpdate test vehicles & impact conditionsEliminated ambiguitiesRemoved inconsistenciesConsolidate test matricesTighten reporting proceduresThe primary focus of the updated criteria that will be contained in the MASH document was to update the test vehicles and impact conditions. In addition ambiguity was eliminated and inconsistencies removed. Some of the test matrices were refined and in some cases tests were eliminated. Furthermore reporting procedures were tightened to require more documentation of test conditions such as soil characteristics.
10Most Significant Changes Small car and Pickup mass increasedTL-4, single unit truck test revisedImpact angle for small car increased to 25oImpact angle for terminals and crash cushions raised to 25oThe most significant changes in the new criteria are the test vehicles, both the small car and pickup truck, increased in mass to better reflect the vehicles on the road. The test level 4 single unit truck test was revised. The impact angle for small cars was increased to 25 degrees and The impact angle for testing terminals and crash cushions was increased to 25 degrees.10
11Small CarThe 820C vehicle specified in Report 350 has not been manufactured since 2000.Proposed vehicle is a 1100C (2420 lb)The mass of the small car has increased since the NCHRP 350 report was first published. The typical 820kg (1800 lb) test vehicle as shown on the left in this picture was a geo metro or a ford festiva. These vehicles have not been manufactured since the 2000 model year. Based on sales data the mass of the small car that represents the 2 percentile has increased to 2420 lb. This means that there are only 2 % of vehicles that are being manufactured and sold that are less than this weight. The typical vehicle with this new weight criteria is the Kia Rio as is shown on the right in this picture. Note that the bumper heights for these vehicles are not significantly different.A common question is Aren’t vehicles going to get lighter with increases in gas prices? It would take years for auto companies to develop lighter cars and it is unlikely that significant numbers of these cars will show up on the highways for some time. In addition, there are additional safety features such as strengthened roofs that will be required in the future that will likely add weight. It should be noted that even hybrid vehicles, like the Toyota Prius, weigh more primarily due to the weight of the batteries. Researchers expect that fuel economies will have to be achieved by means other then reducing the weight of the vehicle.modelscurb weight - 2,765 lb
12Small Car AngleIncrease impact angle from 20 degrees to 25 degrees to be consistent with Pickup testTested with new impact vehicle and angle into a rigid NJ shaped concrete barrierThe angle used for the small car in NCHRP Report 350 for barrier testing was 20 degrees while the angle used with the P/U was 25 degrees. Testing rigid barriers with the small car was considered a challenge at higher angles because of the forces that are exerted on the occupants. As part of the update, a test was conducted with a rigid concrete barrier using the 25 degree angle and it was successful. As a result, the new criteria uses the 25 degree angle impact for both test vehicles.
13Pickup TruckThe 2000P Pickup specified in Report 350 has not been manufactured since 2001Quadcab reflects the 90th percentile vehicleProposed vehicle is a 2270P Quadcab Pickup (5000 lbs)Quadcab Pickup has a higher center of gravity and more closely represents the large SUV’sThe NCHRP Report 350 specified a ¾ ton single cab P/U, as shown on the left that had a mass of 2000 kg (4400 lbs). This vehicle was intended to represent the mini vans and SUV’s that have gained in popularity in the last 20 years. However, the size of these vehicle has grown and a 4400 lb ¾ ton P/U has not been manufactured since the 2001 model year.Research found that the vehicle that represents the 90 percentile for weight of these vehicles in approximately 5000 lbs. This means that approximately 10% of passenger vehicles weigh more than 5000 lbs.In addition, to better represent the larger passenger vehicles, a quadcab truck was selected. As is shown in the photo, the new test vehicle, on the right, typically has a higher bumper and center of gravity than the ¾ ton P/U specified in NCHRP Report 350.
14Pickup TruckHow does w-beam guardrail (27-5/8” height, steel posts) perform with large vehicle?One concern that was raised regarding the use of the larger P/U truck was for whether widely used systems like the W-beam guardrail would pass the test. As part of the development of MASH a test of the w-beam guardrail was run with the new test vehicle. As is seen in the video, the vehicle was redirected and remained upright after impact.
15Pickup TruckHow does w-beam guardrail (27” height, wood posts) perform with large vehicle?One concern that was raised regarding the use of the larger P/U truck was for whether widely used systems like the W-beam guardrail would pass the test. As part of the development of MASH a test of the w-beam guardrail was run with the new test vehicle. As is seen in the video, the vehicle was redirected and remained upright after impact.
16Impact Angle for Terminals and Crash Cushions The angle of impact for the Length Of Need (LON) test for barrier terminals and crash cushions was increased from 20 degrees to 25 degrees for consistency with LON and Transition testsImpact angle for the end-on test of gating terminal decreased from 15 degrees to 5 degrees as it is more criticalIn NCHRP Report 350 the highest test level specified for barrier terminals and crash cushions is TL-3. This did not change with the MASH criteria. However, the test impacting at the beginning of the length of need for barrier terminals and crash cushions was increased from 20 degrees to 25 degrees. This change was made for consistency since it is a strength test and intended to determine the point where the vehicle would be expected to be redirected.525
17New Test Matrices added Variable Message Sign / Arrow Board test matrix added.Longitudinal Channelizing Devices category added.Several new test matrices were developed for devices that didn’t quite fit the traditional NCHRP 350 test conditions. One example of a new matrix would be for variable message signs and arrow boards. While there has been limited testing of these devices, the video demonstrates the potential for a high severity crash. Adding a matrix is intended to encourage designs that would reduce the impact severity. Another example would be for longitudinal channelizing devices. These devices typically are water filled units that may not be able to pass testing as a barrier.
18Test Matrices revisedPickup Truck Test was added for support structures and work zone traffic control devicesIn addition, the pickup truck test was added for support structures like sign supports and work zone traffic control devices. This test was not required previously as it was assumed that the small car test was the most critical. However, research has demonstrated that these devices have potential for penetration of the windshield of light trucks and this test was added to evaluate this risk.
19Test InstallationsInstallation length more definitive (cable barriers 600 ft minimum).Specified the critical impact point for cable barrier testing to be at a post for the pickup truck testThe MASH criteria is more specific on how the test installations are constructed. Minimum lengths of barrier are specified depending on how critical the length is for proper performance. Testing with cable barriers are now required to use a minimum length of 600 feet. This is critical because these systems rely on the tension to control deflection. Larger deflections may be possible as the distance between the anchors increases.MASH also specifies the impact location for the pickup truck test of cable barriers to be at a post as this is considered the most critical test for gauging the potential for override.
20Test Installations Barrier height (max) small car & (min) pickup test. Addition of performance based specs for soil.It is also recommended when testing barriers that have a range of heights allowed, the maximum height allowed be tested with the small car and the minimum height be tested with the pickup. This is to reduce the potential for a small car under-riding a barrier and the pickup truck from over-riding it.The performance based soil spec was included to ensure consistency and reporting of the soils used in the testing.
21Evaluation Criteria Windshield damage criteria to be more objective. Occupant compartment deformation criteria more objective and based on NHTSA dataMaximum roll angle set to 75 degrees.Evaluation criteria is used to gage the survivability of occupants in the test vehicle. The criteria includes limits on forces, vehicle trajectory, and intrusion into the vehicle. The evaluation criteria contained within the MASH is very similar to that found in NCHRP Report 350 with a couple of exceptions. MASH provides more objective criteria for windshield damage because when objects strike the windshield there may be potential for entering the occupant compartment and this criteria gives an indication of the risk of this occurring.MASH also includes criteria for occupant compartment deformation such as floor pan deformation. This criteria was developed using NHTSA’s data that related amount of deformation with injuries sustained. Based on this data more deformation is allowable in the floor pan up to 12 inches as opposed to the roof which is limited to 4 inches.A minor revision also made to a maximum roll angled allowed. NCHRP Report 350 suggested moderate roll angle was allowable. The MASH criteria set the maximum roll angle at 75 degrees.
22Single Unit Truck Test (TL-4) NCHRP Report 350, the impact severity of the SU test (TL-4) is less than the impact severity of the Pickup test (TL-3)Intent was to make the TL-4 test more meaningful.MASHThe single unit truck test which is Test Level 4 was significantly revised in the MASH criteria. When calculating the impact severity the mass speed and angle of impact are the critical factors. The NCHRP Report 350 criteria for test level 4 specifies a lower speed of 50 mph and a lower impact angle of 15 degrees compared to test level 3 test which is conducted at 62 mph and 25 degrees. Even though the mass was higher in test level 4 (18,000 lbs vs. 4,500 lbs) the impact severity was lower than test level 3 with the pickup truck.Note the difference on the graph. With the MASH update the intent was to make the Test Level 4 more meaningful and as shown on the graph the impact severity is raised above the test level 3 conditions.NCHRP 350
23Single Unit Truck Test (TL-4) Mass increased from 8,000 kg (18000 lb) to 10,000 (22,000 lb)Speed increased from 80 km/h (50 mph) to 90 km/h (56 mph)32” New Jersey shaped concrete barrierTo increase the impact severity of the test level 4 test the mass of the truck was increased from 18,000 lbs to 22,000 lbs and the impact speed was increased from 50 mph to approximately 56 mph. In addition the height of the ballast center of gravity was modified and guidance on securing the body to the frame was specified for consistency. As part of the update a test was conducted at the test level 4 conditions with a 32 inch New Jersey shaped bridge rail.As you can see in the video, the vehicle in this test would have gone over the bridge rail and modification of bridge rail designs may need to be considered to meet the MASH TL-4 test.
24Single Unit Truck Test (TL-4) 36” Single Slope concrete barrierTo increase the impact severity of the test level 4 test the mass of the truck was increased from 18,000 lbs to 22,000 lbs and the impact speed was increased from 50 mph to approximately 56 mph. In addition the height of the ballast center of gravity was modified and guidance on securing the body to the frame was specified for consistency. As part of the update a test was conducted at the test level 4 conditions with a 32 inch New Jersey shaped bridge rail.As you can see in the video, the vehicle in this test would have gone over the bridge rail and modification of bridge rail designs may need to be considered to meet the MASH TL-4 test.
25What did not change?Impact speed for high speed test retained at 100 km/h (62 mph)No Changes to TL-5 and TL-6Angle for strength testSix test levelsThere are several items of note that did not change in the update. First the high speed used in test level 3 was retained at 100km/h or 62 mph and this test level is considered the basic level for high speed facilities even though they may have posted speeds in excess of these test conditions. As discussed earlier the speed used in the testing is not directly related to the posted speeds of the highways the devices will be installed.The combination of high angle and high speed represents a significant impact and while some vehicles may exceed the angle or speed very few exceed both. There were no changes to test level 5 and 6 that use a tractor trailer and tanker truck. The angle for the strength test was retained at 25 degrees and the number of test levels was retained at 6.
26Tests Conducted with New Criteria W-Beam Guardrail – Steel Post (27-5/8” height)Pickup (passed)W-Beam Guardrail – Wood Post (27” height)Pickup (failed)As discussed previously there was quite a bit of testing conducted during the development of the MASH document. We saw the video earlier of the W-Beam Guardrail testing with the new pickup truck. In addition the Midwest guardrail system which utilizes the standard W-Beam rail but is mounted at 31 inches to the top of the rail, uses deeper block outs, and splices that are offset from the posts was successfully tested with both the pickup truck and the small car. The video shows the test with the MASH pickup.In addition a guardrail transition was tested with the pickup and the critical impact point on a guardrail terminal was tested with the small car. Both were successful
27Tests Conducted with New Criteria Box-Beam GuardrailPickup (passed)Weak Post W-BeamMidwest Guardrail (31” height)Small Car (passed)As discussed previously there was quite a bit of testing conducted during the development of the MASH document. We saw the video earlier of the W-Beam Guardrail testing with the new pickup truck. In addition the Midwest guardrail system which utilizes the standard W-Beam rail but is mounted at 31 inches to the top of the rail, uses deeper block outs, and splices that are offset from the posts was successfully tested with both the pickup truck and the small car. The video shows the test with the MASH pickup.In addition a guardrail transition was tested with the pickup and the critical impact point on a guardrail terminal was tested with the small car. Both were successful
28Tests Conducted with New Criteria W-Beam Guardrail Median BarrierPickup (failed)Small Car (passed)Thrie Beam Guardrail BarrierGuardrail TransitionPickup (passed)Guardrail Terminal (SKT)CIP test with small car (passed)As discussed previously there was quite a bit of testing conducted during the development of the MASH document. We saw the video earlier of the W-Beam Guardrail testing with the new pickup truck. In addition the Midwest guardrail system which utilizes the standard W-Beam rail but is mounted at 31 inches to the top of the rail, uses deeper block outs, and splices that are offset from the posts was successfully tested with both the pickup truck and the small car. The video shows the test with the MASH pickup.In addition a guardrail transition was tested with the pickup and the critical impact point on a guardrail terminal was tested with the small car. Both were successful
29Tests Conducted with New Criteria Rigid 32” NJ shape concrete barrierSmall car (passed)Single Unit Truck (fail as TL-4)Precast Concrete Barrier (Iowa F Shape)Pickup (passed)Several test were also conducted with concrete barriers. Previously you saw the tests with the small car and single unit truck hitting a 32 inch rigid New Jersey shaped concrete barrier. The video you are watching now is a test of a precast f-shape barrier with a pickup truck. It was successfully contained and redirected in this test.
30Tests Conducted with New Criteria U Channel sign supportPickup (passed)Perforated square tube sign suppostPickup (failed)Several test were also conducted with concrete barriers. Previously you saw the tests with the small car and single unit truck hitting a 32 inch rigid New Jersey shaped concrete barrier. The video you are watching now is a test of a precast f-shape barrier with a pickup truck. It was successfully contained and redirected in this test.
31MASH Implementation Plan AASHTO Technical Committee on Roadside Safety (TCRS) is responsible for developing and maintaining MASH.FHWA shall review and accept highway safety hardware under MASH.As the MASH document was being finalized the AASHTO technical committee on Roadside Safety worked with the FHWA to develop an implementation plan. This plan designates the Technical Committee on Roadside Safety (TCRS) as being responsible for developing and maintaining MASH andalso specifies that FHWA will continue its service of reviewing and issuing acceptance letters for hardware that has been tested using the MASH criteria.
32MASH Implementation Plan All hardware accepted under Report 350 may remain in place and may continue to be manufactured and installed.Hardware accepted using Report 350 is not required to be retested using the MASH criteriaIn the implementation plan it was recognized that devices that were developed and tested using Report 350 criteria were generally performing acceptably and the implementation plan allows for the continued use, manufacturing and new installation of these devices without retesting.
33MASH Implementation Plan However …If hardware that met Report 350 is tested and fails using MASH…AASHTO & FHWA will jointly review results and determine a course of action.?NCHRP 350However, if a device that met Report 350 is retested using the MASH criteria and fails, it was agreed that the AASHTO Technical Committee on Roadside Safety and FHWA will jointly review the results and determine a course of action. This action could be to accept continued use of the device, pursue additional research to evaluate the in-service performance or to recommend discontinuing the use of the device if suitable alternatives are available.MASHFail PassFail Pass
34MASH Implementation Plan Upon adoption new hardware not previously evaluated shall utilize the MASH criteriaHardware under development at time of AASHTO adoption can be completed under Report 350FHWA will not consider applications for acceptance under Report 350 after January 1, 2011.Upon adoption by AASHTO all new hardware that has not been previously evaluated shall be evaluated using the new MASH criteriaHardware that was under development at the time that AASHTO adopts MASH can be completed under NCHRP Report 350.However, the FHWA will no longer consider applications for acceptance of devices developed using NCHRP 350 after January 1, 2011.
35MASH Implementation Plan Hardware installed on new or reconstruction projects shall meet Report 350 or MASHAgencies are encouraged to upgrade hardware that does not meet Report 350 or MASH when:roadway is reconstructed3R projectsSystem damaged beyond repairWhen adopted all safety hardware that is installed as part of new construction or reconstruction projects shall meet either the NCHRP Report 350 or MASH criteria.The implementation plan also recommended that hardware that did not meet Report 350 or MASH should be upgraded when the roadway is reconstructed subject of a 3R project or when the system is damaged beyond repair.
36MASH Implementation Plan Hardware not meeting either Report 350 or MASH and for which there are no suitable alternatives can remain in place and can continue to be installed.The implementation plan also recognized that there are some hardware classes where NCHRP Report 350 devices had never been developed and tested. The implementation plan allows for continued use of these systems until a design that meets either MASH or report 350 becomes available. An example of this is the weak post intersection design as shown in the picture.
37Contact InformationFHWA Office of SafetyNick ArtimovichPhone:Will LongstreetPhone:FHWA Resource CenterDick AlbinPhone:FHWA Roadside Hardware LinkThis concludes the overview of the crash criteria for roadside hardware. However, if you have any questions on the MASH criteria or roadside hardware in general, you can contact Nick Artimovich or Will Longstreet in the FHWA Office of Safety or me Dick Albin in the FHWA Resource Center Safety and Design Team. Additional information can be found on the FHWA safety website via the link shown below.Thank you and stay on the road.
38A narrated presentation can be viewed by following this link: https://admin.na3.acrobat.com/_a /mashfinal/