Product and Installation Manual: Sentry Barrier TL-4 ThrieBeam System
ACP
| September 2020 |
Page
12
New South Wales
Sydney
02 8708 4400
Victoria
Melbourne
02 8708 4400
Queensland
Brisbane
07 3442 6200
Western Australia
Perth
02 9772 4172
Length of Need
The minimum Length of Need (LoN) of the
Sentry Barrier TL-4 ThrieBeam System
is dependent on
the specific hazard being protected and the posted speed limit. The default Length of Need (LoN)
determined through crash testing is 86.0m excluding transitions and terminal ends, however, refer to
state roading authority approval letters for local minimum length requirements where applicable.
Designers should also refer to the Austroads Guide to Road Design
– Part 6, Section 6.3, for
detailed design process of barrier length run required.
For sites where geometric constraints exist, designers may require shorter length of need, in such
instances, a 12m* length of need for TL-3 containment design can be utilised plus the length of the
transition and terminal end regions on either end of the barrier system. For TL-4 containment design,
a 20m* length of need can be utilised plus transition and terminal end regions. We recommend
designers or Installers contact their local Roading Control Authority for further information or
guidance if required.
* These lengths have been calculated based upon the actual vehicle contact lengths from the
respective Test 4-11 and Test 4-12 crash test articles noted in the crash test report.
System Deflection
The transverse deflection of a barrier during a crash is dependent upon the mass, speed, and impact
angle of the errant vehicle. The maximum levels of dynamic deflections measured during impact
testing are presented below.
Test 4-10
Test 4-11
Test 4-12
Vehicle Type
Car
Pick up
Truck
Vehicle Mass
1,100 kg
2,270 kg
10,000 kg
Vehicle Speed
100 km/hr
100 km/hr
90 km/hr
Impact Angle
25°
25°
15°
Dynamic Deflection
1.06 m
1.45 m
1.53 m
Crash testing typically represents the extremes impact parameters. A review of the proposed barrier
location can be undertaken to assess the following variables influence on the likely maximum system
deflection;
• Maximum attainable impact angle;
• Design speed; and
• Design vehicle.
Note
:
The TL-3 containment level is measured in Test 4-11 i.e. Dynamic Deflection of 1.45m.
The TL-4 containment level is measured in Test 4-12 i.e. Dynamic Deflection of 1.53m
