1. Bumper Trajectories During High-Speed Impacts with 6-in. Curbs
Ronald K. Faller, Ph.D., P.E.
Midwest Roadside Safety Facility (MwRSF)
University of Nebraska-Lincoln
TRB Committee AFB 20
June 15-18, 2008
Jackson, Wyoming

2. Introduction
MGS placed 6 in. (mid-face) behind 6-in. high, AASHTO Type B curb met TL-3 of NCHRP 350
Pooled Fund States sponsored study to determine performance limits of MGS behind 6-in. curbs
allow for some variability in MGS placement
allow for sidewalk placement in front of MGS
reduce snow plow impacts with rail & resulting damage
determine lateral offset when MGS needs to be raised
Obtain bumper trajectories for curb impacts with pickup trucks and small cars
Evaluate critical MGS offsets using MASH 08

3. MGS w/ 6-In. Curb (Test NPG-5)
The W-beam rail was 6-in. behind the curb front face.
The system successfully contained and redirected the 2000P pickup.

4. Bumper Trajectory Test Set-up
Location: MwRSF test field in Lincoln
Test set-up: 6-in. AASHTO Type B curb
Test Speed: 100 km/h
Test Angle: 25 degrees
Speed and angle believed to provide worst case impact scenario for vaulting vehicles in advance of MGS.

5. Vehicle-Curb Test - MGSC-1 (2270P)
4,966 lbs
62.2 mph
25 deg

6. Vehicle-Curb Test - MGSC-2 (2270P)
4,966 lbs
62.6 mph
25 deg
Same 2270P vehicle used for second 2270P test.

7. Vehicle-Curb Test - MGSC-3 (1100C)
2,544 lbs
61.6 mph
25 deg
2002 Kia Rio (1100C)

8. Wheel Damage - MGSC-3 (1100C)
There were no damages to the 2270P and 2000P pickups, except minor tire scraches.
3 tires were aired out for 1100C with rim bent.

9. Vehicle-Curb Test - MGSC-4 (2000P)
High-speed impact with 6-in. curb has negligible effect on vehicle’s path.
4,479 lbs
62.5 mph
25 deg

10. Curb-Lateral Coordinate System
To bring the film analysis data into phase and to show the offset of possible MGS installation, a new coordinate was set up.

11. Critical Override Impact Point
Critical Point
The critical override impact point was determined to be the top edge of the pickup bumper. The W-beam guardrail can capture the pickup as long as the bumper top edge is lower than the W-beam top hump.
This geometry was analyzed from the previous full-scale crash tests and also was verified by LS-Dyna simulation. However, this is a conservative criteria. Under certain situations, the guardrail can still contain the pickup without engaging its bumper.
The top edge trajectory was transformed from the bumper target trajectory.
Critical Point

13. Small Car underride analysis was based on the impact height from test MG-3.
The small car was considered safe if its impact height is higher than the impact height in MG-3.
If the small car’s impact height is lower than MG-3, there is a chance that a small car might underride the MGS.

14. Predicted Safe Zones – 31” MGS
Considering 2000P, the safe zone is before 3.71 ft.
Only considering 2270P, the safe zone is before 4.23 ft.
Both the pickup and small car used conservative analysis. There might be a chance that the MGS can still capture vehicles in some of the unsafe zones.

15. Predicted Safe Zones – 37” MGS
The safe zone is between 3.14 ft and 8.3 ft.