All road safety barrier hardware is subject to compliance testing to ensure that it performs satisfactorily for typical crash conditions. These input conditions are representative of the vehicle fleet and impact characteristics and relate to the development and containment of crash energy - a function of vehicle mass, speed and angle of impact.
There has been a gradual progression in compliance standards in New Zealand. In 1999 the U.S. National Cooperative Highway Research program (NCHRP) Report 350 was adopted by the then Transit NZ, succeeding NCHRP Report 230. Since November 2012 all new systems (and significant variants of existing systems) submitted to the New Zealand Transport Agency (Transport Agency) for acceptance are required to meet the American Association of State Highway and Transportation Officials (AASHTO) Manual for Assessing Safety Hardware (MASH) compliance requirements.
All road safety barrier hardware submitted and accepted by the Transport Agency prior to that date has been grandfathered. What this means is that NCHRP 350 hardware remains equally acceptable for use on State Highways as the more recent MASH hardware - subject to meeting the location specific containment requirements.
A system compliant to a MASH containment test level (e.g. TL-3) is considered to have met the same NCHRP 350 test level (i.e. TL-3). There are systems that have been accepted for both NCHRP 350 and MASH containment test levels and in those cases both acceptances are relevant (e.g. MASH TL-3 for the 2270kg pickup and NCHRP 350 TL-4 for the single unit truck).
The differences between NCHRP 350 and MASH reflect the upsizing of the American vehicle fleet since 1999 and amendments to remove testing inconsistencies in impact conditions and evaluation criteria in NCHRP 350.
The MASH fleet characteristics are generally similar to the New Zealand light vehicle fleet. However, the New Zealand High Productivity Motor Vehicles (HPMV), with masses above 44 tonnes, exceed the mass for TL-5 and TL-6 test regimes. Barriers at these test levels may not provide containment for these larger vehicles when the impact speed and angle are met or exceeded.
The key differences between the two test protocols are:
- Pickup truck mass increases from 2000kg to 2270kg
- Small car mass increases from 820kg to 1100kg
- Small car impact angle increases from 20 to 25 degrees
- TL-4 truck mass increases from 8,000kg to 10,000kg
- TL-4 truck speed increases from 80kph to 90kph
- Terminal and crash cushion impact angle increases from 20 to 25 degrees.
The NCHRP 350 and MASH impact conditions and containment energy for the highest mass vehicle are summarised in the following tables. Lighter weight vehicles (820kg for NCHRP 350 and 1100kg for MASH) are also used in all tests to ensure that impact severity conditions are not exceeded for these smaller vehicles.
NCHRP 350 Summary
- Transport Agency accepted NCHRP 350 tested and compliant products can still be used on State Highways
- All new systems (and significant variants of existing systems) submitted to the Transport Agency for acceptance after November 2012 have to meet MASH compliance testing
- When an NCHRP 350 Test Level (e.g. TL-3) is stipulated then either a higher NCHRP 350 (e.g. TL-4) or MASH equivalent or higher test levels (e.g. TL-3 or TL-4) can be used
- Accepted hardware compliant to both NCHRP 350 and MASH containment test levels are relevant to the test vehicle and impact conditions.