1200 New Jersey Avenue, SE. 

Washington, DC 20590

March 20, 2009 

 In Reply Refer To: HSSD/B-189 

Mr. Ronald K. Faller, Ph.D. 

Research Assistant Professor 

Midwest Roadside Safety Facility (MwRSF) 

University of Nebraska-Lincoln 

527 Nebraska Hall 

Lincoln, NE 68588-0529 

Dear Dr. Faller: 

This letter is in response to your request for Federal Highway Administration (FHWA) 

acceptance of a roadside safety system for use on the National Highway System (NHS). 

Name of system: Midwest Guardrail System (MGS) for Long-Span Culvert 

Applications 

Type of system: Longitudinal Barrier 

 Test Level: Manual for Assessing Safety Hardware (MASH) TL-3 

 Testing conducted by: Midwest Roadside Safety Facility 

 Date of request: June 25, 2008 

 Date of completed package: February 06, 2009 

You requested that we find this system acceptable for use on the NHS under the provisions of 

National Cooperative Highway Research Program (NCHRP) Report 350 “Recommended 

Procedures for the Safety Performance Evaluation of Highway Features” 

Requirements 

Roadside safety systems should meet the guidelines contained in the NCHRP Report 350. The 

FHWA Memorandum “ACTION: Identifying Acceptable Highway Safety Features” of 

July 25, 1997, provides further guidance on crash testing requirements of longitudinal barriers. 

System Description, Test number LSC-1 

The MGS long-span design consisted of 55.25 m (181.25 ft) of standard 2.67 mm (12 gauge) 

thick W-beam guardrail supported by steel posts and six CRT posts. Anchorage systems similar 

to those used on tangent guardrail terminals were utilized on both the upstream and downstream 

ends of the guardrail system. 
2

The entire system was constructed with twenty-six guardrail posts. Post numbers 3 through 10 

and 17 through 24 were galvanized ASTM A36 steel W152 x 13.4 (W6 x 9) sections measuring 

1,829 mm (72.0 in.) long. Post numbers 1, 2, 26, and 27 were BCT timber posts measuring 

140 mm wide x 190 mm deep x 1,080 mm long (5.5 in. wide x 7.5 in. deep x 42.5 in. long) and 

were placed in 1,829 mm (72.0 in.) long steel foundation tubes. The timber posts and foundation 

tubes were part of anchor systems designed to replicate the capacity of a tangent guardrail 

terminal. Post numbers 11 through 16 were 152 mm wide x 203 mm deep x 

1,829 mm long (6.0 in. wide x 8.0 in. deep x 72.0 in. long) timber, breakaway CRT posts. 

Post numbers 3 through 24 were spaced 1,905 mm (75.0 in.) on center with a soil embedment 

depth of 1,016 mm (40.0 in.). Three posts were omitted in the center section of the guardrail to 

create a 7.62 m (25.0 ft) long, unsupported guardrail length in the center of the system. The 

posts were placed in a compacted coarse, crushed limestone material that met Grading B of the 

American Association of State Highway and Transportation Officials M147-65 (1990) as found 

in NCHRP Report Number 350. For post numbers through 24, 152-mm wide x 305 mm deep x 

362-mm long (6.0 in. wide x 12.0 in. deep x 14.25 in. long) wood spacer block outs were used to 

block the rail away from the front face of the steel and CRT posts. 

Standard 2.67 mm (12 gauge) thick W-beam rails with additional post bolt slots at half post 

spacing intervals were placed between post numbers 1 and 29. The nominal top mounting height 

of the W-beam rail was 787 mm (31.0 in.) with a 632 mm (24.875 in.) center height. The rail 

splices have been moved to the center of the span location. All lap splice connections between 

the rail sections were configured to reduce vehicle snag at the splice during the crash test. No 

nested guardrail sections were used in the MGS long-span design. 

For test number LSC-1, a simulated culvert headwall was constructed behind the MGS 

long-span guardrail in order to simulate any potential vehicle drop off of the edge of the culvert 

and to simulate the effect of the culvert headwall on the deflection of adjacent guardrail posts 

during an impact. The design of the headwall was based on a survey of common culvert designs 

from the sponsoring agencies. The simulated culvert headwall consisted of a 229 mm thick x 

1,219 mm tall (9.0-in. thick x 48.0 in. tall) reinforced concrete wall installed 305 mm (12.0 in.) 

behind the back of the CRT posts in the system or 898 mm (35.35 in.) behind the face of the rail. 

The headwall ran parallel to the guardrail from 1,219 mm (48.0 in.) downstream of post number 

13 until 305 mm (12.0 in.) upstream of post number 14. At 305 mm (12.0 in.) upstream of post 

number 14, the headwall angled away from the guardrail at a 45 degree angle for 1,805 mm 

(71.0 in.) to form the downstream wing wall of the culvert. The top of the simulated concrete 

headwall was installed at the ground height for the guardrail system and a 1,219 mm (48.0 in.) 

deep pit was excavated behind the headwall to create the necessary drop-off. The soil around the 

culvert headwall and the top of the headwall itself remained level for this installation in order to 

simplify the installation. This simplification could be made because crash testing was designed 

to evaluate the capacity of the system by eliminating any adverse interaction of vehicle and 

culvert head wall by maintaining an at-grade head wall height. 

Crash Testing, Test Number LSC-1 

The analysis of the crash test results showed that the MGS long-span guardrail adequately 

contained and redirected the vehicle with controlled lateral displacements of the guardrail. 

Detached elements and debris from the test article did not penetrate nor show potential for 
3

penetrating the occupant compartment. Deformations of, or intrusion into, the occupant 

compartment that could have caused serious injury did not occur. The vehicle remained upright 

during and after collision. Vehicle roll, pitch, and yaw angular displacements were noted, but 

they were deemed acceptable because they did not adversely influence occupant risk safety 

criteria nor cause rollover. It is noted that the occupant impact velocities (OIV) and occupant 

ride down decelerations (ORD) were within the suggested limits provided in the update to 

NCHRP Report Number 350. After collision, the vehicle’s trajectory intruded slightly into 

adjacent traffic lanes but was determined to be acceptable. In addition, the vehicle exited the 

barrier within the exit box. Therefore, test number LSC-1 conducted on the MGS long-span 

guardrail system was determined to be acceptable according to the update to NCHRP Report 

Number 350 criteria. It should also be noted that this test successfully evaluated the strength 

capacity of the system through the choice of a critical impact point that maximized the potential 

for pocketing, wheel snag, and rail rupture and the use of the 2270P vehicle to maximize rail 

loading.

System Description, Test Number LSC-2 

The design of the MGS long-span guardrail remained unchanged for test number LSC-2, but 

modifications were made to the design of the culvert and the lateral offset between the guardrail 

and the culvert headwall. Since the purpose of test number LSC-2 was to evaluate the hazard 

posed by an impact that maximized the interaction between the vehicle and the culvert wall, a 

more detailed, representative culvert headwall was developed for this test. Additionally, the 

dynamic deflection and vehicle trajectory of the previous test, test number LSC-1, led the 

researchers to believe that the lateral offset between the barrier and the culvert headwall could be 

further reduced. 

The culvert design was modified to include both the upstream and downstream wing walls as 

well as a typical slope profile based on representative culvert designs submitted by the 

sponsoring agencies. The culvert consisted of a 229-mm thick x 1,219-mm tall (9.0-in. thick x 

48.0-in.) reinforced concrete wall installed flush with the back of the CRT posts in the system or 

591 mm (23.25 in.) behind the face of the rail. The headwall ran parallel to the guardrail from 

305 mm (12.0 in.) downstream of post number 13 until 305 mm (12.0 in.) upstream of 

post number 14. At 305 mm (12.0 in.) upstream of post number 14 and 305 mm (12.0 in.) 

downstream of post number 13, the headwall angled away from the guardrail at a 45 degree 

angle for 1,819 mm (71.61 in.) to form the wing wall of the culvert. The top of the simulated 

concrete headwall was installed at the ground height for the guardrail system. A 3:1 slope was 

started 610 mm (24.0 in.) behind the back face of the guardrail posts of the MGS long-span, and 

the wing walls were modified to match the soil slope. The choice of the slope profile was based 

on choosing the flattest slope of the typical culvert installations submitted by the sponsoring 

states. The choice of the flattest slope maximized the potential for vehicle interaction with the 

wing walls of the culvert during the impact event. A 1,219 mm (48.0 in) deep pit was excavated 

behind the headwall to create the necessary drop-off. 

Crash Testing, Test Number LSC-2 

The analysis of the test results for test number LSC-2 showed that the MGS long-span guardrail 

adequately contained and redirected the vehicle with controlled lateral displacements of the 

guardrail. Detached elements and debris from the test article did not penetrate nor show 
4

potential for penetrating the occupant compartment. Deformations of, or intrusion into, the 

occupant compartment that could have caused serious injury did not occur. The vehicle 

remained upright during and after collision. Vehicle roll, pitch, and yaw angular displacements 

were noted, but they were deemed acceptable because they did not adversely influence occupant 

risk safety criteria nor cause rollover. It is noted that the OIV and ORD were within the 

suggested limits provided in the update to NCHRP Report Number 350. After collision, the 

vehicle’s trajectory intruded slightly into adjacent traffic lanes but was determined to be 

acceptable. In addition, the vehicle did not exit the barrier within the exit box, but the trajectory 

of the vehicle was deemed acceptable. Therefore, test number LSC-2 conducted on the MGS 

long-span guardrail system was determined to be acceptable according to the update to the 

NCHRP Report Number 350 criteria. It should be noted that this test successfully evaluated the 

potential for vehicle instability through the choice of a CIP that maximized the impact of the 

left-front wheel on the upstream wing wall of the culvert. Additionally, the 0-mm (0-in.) offset 

from the back of the posts to the front face of the culvert headwall did not adversely affect the 

safety performance of the system and was believed to be a reasonable minimal offset distance for 

the MGS long-span based on this test. It is not believed that the reduced barrier offset in this test 

would have had any effect on the outcome of test number LSC-1, which focused on the rail 

capacity of the system and not vehicle interaction with the culvert. 

Findings 

Therefore, the MGS for Long-Span Culvert Applications system described above and detailed in 

the enclosed drawings is acceptable for use on the NHS under the range of conditions tested, 

when such use is acceptable to a highway agency. 

Please note the following standard provisions that apply to the FHWA letters of acceptance: 

 This acceptance is limited to the crashworthiness characteristics of the systems with respect 

to at-grade headwall weights only and does not address all other height conditions of an 

existing headwall. 

 This acceptance is limited to the crashworthiness characteristics of the systems and does not 

cover their structural features, nor conformity with the Manual on Uniform Traffic Control 

Devices. 

 Any changes that may adversely influence the crashworthiness of the system will require a 

new acceptance letter. 

 Should the FHWA discover that the qualification testing was flawed, that in-service 

performance reveals unacceptable safety problems, or that the system being marketed is 

significantly different from the version that was crash tested, we reserve the right to modify 

or revoke our acceptance. 

 You will be expected to supply potential users with sufficient information on design and 

installation requirements to ensure proper performance. 

 You will be expected to certify to potential users that the hardware furnished has essentially 

the same chemistry, mechanical properties, and geometry as that submitted for acceptance, 

and that it will meet the crashworthiness requirements of the FHWA and the NCHRP 

Report 350. 
5

 To prevent misunderstanding by others, this letter of acceptance is designated as number 

B-189 and shall not be reproduced except in full. This letter and the test documentation upon 

which it is based are public information. All such letters and documentation may be 

reviewed at our office upon request. 

 This acceptance letter shall not be construed as authorization or consent by the FHWA to use, 

manufacture, or sell any patented system for which the applicant is not the patent holder. 

The acceptance letter is limited to the crashworthiness characteristics of the candidate 

system, and the FHWA is neither prepared nor required to become involved in issues 

concerning patent law. Patent issues, if any, are to be resolved by the applicant. 

Sincerely yours, 

David A. Nicol 

Director, Office of Safety Design 

Office of Safety 

FHWA:HSSD:WLongstreet:tb:x60087:3/3/09 

File: s://directory folder/wlongstreet/B189-MwRSF Research Report No TRP-03-187-07 

 022609.doc 

cc: HSSD (Reader, HSA; Chron File, HSSD; W.Longstreet, HSSD; NArtimovich, HSSD; 

 MMcDonough, HSSD) 
(TYP.)

28 Spaces @ 75"=2100"

 75"

40'

25°

24"

MGS_Longs

DWG. NAME.

Midwest Roadside Safety Facility

MGS 

System 

BCT posts in 6' long (galvanized) foundation tubes, ground line strut, and BCT cable anchor

W6x9 72" long Posts with 6x12x14 1/4" Blockouts CRT 6x8x72" long Wood Posts 11-16 with 6x12x14 1/4" Blockouts

PROFILE VIEW

End Section 

12-gauge

W-Beam Section

 or Two 12'-6"

12-gauge

Section,

W-Beam

150"

12-gauge

Section,

W-Beam

150"

12-gauge

Section,

W-Beam

150"

12-gauge

Section,

W-Beam

150"

12-gauge

Section,

W-Beam

150"

12-gauge

Section,

W-Beam

150"

12-gauge

Section,

W-Beam

150"

12-gauge

Section,

W-Beam

150"

12-gauge

Section,

W-Beam

150"

Section

W-Beam

300" 150"

12-gaug

31" B

B

JJ

AA

PP

2 3 5 4 6 7 8 9 10 11 16 

12 13

1 14 15 17 18 19 20 2

PLAN VIEW

Soil Cut 3:1 3:1

100' 3:1 Cut

SECTION P-P

Top of Concrete Header At Grade

36"

31"

48"

SECTION J-J

31"
MGS_Longs

DWG. NAME.

Midwest Roadside Safety Facility

MGS 

Soil Cu

12 13 1

Concrete Header

PLAN VIEW

Excavated Pit 3:1 

12"

9"

12"

270"

45°

50 1/4" 5

24" 

34"
24"

 32"

(TYP)

5 

Bill of Bars

Item No. QTY. Description Material Specification

- 1 Concrete Header f'c=4000 ksi

b1 6 #4 Bar - Longitudinal - 270" long Grade 60 Steelb2 12 #4 Bar - Bent Longitudinal - 80" long Grade 60 Steelb3 30 #4 Bar - Transverse - 45" long Grade 60 Steel

MGS_Longs

DWG. NAME.

Midwest Roadside Safety Facility

MGS 

Concre

b3

45"

b1

PLAN VIEW

4.24:1 Slope

H

270" 50 1/4"

45°

9"

2" 50 1/4"

b1

b3

PROFILE VIEW

b2

1" chamfer 14" Min. Lap

 17"

(TYP)

II

b2 NOTE:

All bars are Grade 60 No. 4 

66"

14"

R2"

48

2 

b1

270"
48 1/4"

MGS_Longs

DWG. NAME.

Midwest Roadside Safety Facility

MGS 

MGS_Longs

DWG. NAME.

Midwest Roadside Safety Facility

MGS 

End RaSplice 

5/8" Std. Guardrail splice bolts

a1

a2

SPLICE DETAIL

e1

5/8" x 21" Guardrail Post 

Bolt

5/8"x10" Guardrail 

Post Bolt

C 3/4"x2 1/2"

Rail Slot

b1

b2

c1

d1

END RAIL DETAIL

c2

5/8"x10" Guardrail 

Post Bolt

Post 2 

DETAIL C 

SCALE 1 : 15
MGS_Longs

DWG. NAME.

Midwest Roadside Safety Facility

MGS 

Post 317-24 W6x9 

PLAN VIEW

SIDE VIEW

72"

W6x9-Beam Post

Part a1

PROFILE VIEW

1"

3/4"

7 1/8"

3/4"

1"

1/4"

12"

W-Beam Blockout

Part a2

7 1/8" 3/4"

14 1/4"

6"

1 3/4"

SECTION A-A

long Guardrail Post Bolt 5/8"x14" 16D 

Head 

31"
MGS_Longs

DWG. NAME.

Midwest Roadside Safety Facility

MGS 

Post 1CRT W

CRT Wood Post

Part e1

PROFILE VIEW

72"

6"

7 1/8"

3/4"

SIDE VIEW

8"

32"

15 3/4"

3 1/2"

PLAN VIEW

long Guardrail 

SECTION B

Post Bolt a2

5/8"x22" 

31"
MGS_Longs

DWG. NAME.

Midwest Roadside Safety Facility

MGS 

BCT TiFounda

PROFILE VIEW

BCT (MGS) Timber Post Part b2

3/4"

5 1/2"

2 3/4"

46"

7 1/8"

23 7/8"

7/8"

SIDE VIEW

17"

8"

4"

PLAN VIEW

SIDE VIEW

3 3/4"

28 1/2"

2 1/2"

7 1/2"

Foundation Tube

Part b1

PROFILE VIEW

3"

6"

3/4"

1"

72"

PLAN VIEW

TS 8x6x0.1875
MGS_Longs

DWG. NAME.

Midwest Roadside Safety Facility

MGS 

BCT An

Anchor Cable

Bearing Plate Part d2

SIDE VIEW

8"

4"

5"

8"

1 1/8"

PROF

BCT Anchor Cable

Part d1

Cable End

1" Washer A325

D

50"80"

DETAIL D 

SCALE 1 : 5

1"-8UNC ThreadedEntire Length

7" 5"

1 1/2" 1 1/4"

15"
75"

MGS_Longs

DWG. NAME.

Midwest Roadside Safety Facility

MGS 

Ground Bracke

Strut Detail

C6x8.2

3"

6"

R1"

67"

5 1/2"

8 1/4"

R3/8"

1/4"

PROFILE VIEW

Ground Strut

Part c1

78"

PLAN VIEW

Strut

Yoke

R3/8" 

16"

4" 4" 4"

Yoke Detail

Anchor Bracket

Part c2

R1/2"x2"

4"

Anchor Bracke

Bearing Plate Part c3

1 1/2"

2 3/4"

3"

1 1/8"

1 3/8"
93"

75" (TYP)

MGS_Longs

DWG. NAME.

Midwest Roadside Safety Facility

MGS 

Rail Se

25' W-Beam Section, 12 gauge, End Section

G

 (TYP)

312 1/2"

43 3/4"

3/4"x2 1/2" Slots

12'-6" W-Beam Section, 12 gauge

162 1/2"

FF

6'-3" W-Beam Section, 12 gauge

E

87 1/2"

SECTION F-F

DET

SCALE 

DETA

SCALE