US. Deparlmen1 Memorandum 

of Trmsportalion 

Federal Highway 

Admlnls1rallon 

Subject: 

From: 

ACTION: Minnesota DOT Braced Leg 

Sign Support Eligibility Letter SS-170 

MichaelS. Griffith ~ j_ 

Director, Office of Safety Technologies 

Office of Safety 

Date: U1

/ 3 0 

In Reply Refer To: 

HSST 

To: William Stein, Safety Engineer 

Minnesota Division 

This memorandum is in response to your request for the Federal Highway Administration 

(FHWA) to review a roadside safety system for eligibility for reimbursement under the 

Federal-aid highway program. 

Name of system: 

Type of system: 

Test Level: 

Testing conducted by: 

Date of request: 

Date of completed package: 

Initially acknowledged: 

Decision 

Minnesota Type "C" and "D" Braced Leg Sign 

Supports 

U-Channel Sign Support System 

NCJ-JRP Report 350 Test Level 3 

Texas Transportation Institute. 

November 23, 20 I 0 

September 26, 20 12 

December 13, 20 I 0 

The following device is eligible, with details provided below and in the drawings attached 

as an integral part of this memorandum: 

• Minnesota Type 'C" and "D" Braced Leg U- hannel Sign Supports 

Based on a review of crash test results submitted certifying the device described herein 

meets the crash test and evaluation criteria of the National Cooperative Highway Research 

Program (NCHRP) Report 350, the device is eligible for reimbursement under the 

Federal-aid highway program. Eligibility for reimbursement under the Federal-aid 

highway program does not establish approval or endorsement by the FHW A for any 

patiicular purpose or use. 

The FHWA, the Department ofTransportation, and the United States Government do not 

endorse products or services and the issuance of a reimbursement eligibility letter is not an 

endorsement of any product or service. 
Requirements 

To be found eligible for Federal-aid funding, roadside safety devices should meet the 

crash test and evaluation criteria contained in the NCHRP Report 350 or the American 

Association of State Highway and Transportation Officials' Manual for Assessing Safety 

Hardware (MASH). 

Description 

You requested that we review this system using two posts within a seven-loot span under 

the provisions of the NCHRP Report 350. 

2 

The dual-post test installation consisted of an 8-loot wide by 7-foot tall plywood sign 

panel mounted on two steel U-channel supports spaced 39 inches apart. The supports were 

joined in a nested splice with two stubs driven into "strong soil." The stubs were 84 

inches long with an embedment depth of 42 inches. The length of the structural splice 

between the stub and the sign riser post was 30 inches. with the bottom of the riser post 12 

inches above ground level. Structural splices lor u-channcl posts should be a minimum of 

18-inches long with two fasteners at each end of the splice piece. 

The sign supports were braced with two additional supports posts mounted diagonally at a 

slope of~: 1 to the rear of the installation. The braces were attached to the front supports 

with A-frame brackets at the sign panel and anchored to two 48-inch stubs, located 5 feet, 

3 inches behind the front support stubs at 27-inch on center spacing. The rear stubs were 

also driven into the crushed limestone to a depth of 44 inches leaving 4 inches projecting 

above ground level. 

All posts and stubs were 2.5 pound-per-foot rerolled rail steel u-channel posts. Stub-post 

connections and posts splices were joined with 5/l6-inch by 1 ~-inch alloy bolts, nuts, 

and washers. Both posts were struck during the crash tests. A drawing of the test 

installation is enclosed for reference. 

Later crash testing of a three-post supp011 used a similar design with 3-pound-per-foot 

posts. but only two of the supports were impacted. Additional posts may be used to 

support wider signs, but no two posts may be closer than 7 feet. 

Crash Testing 

Four tests were conducted under NCHRP Report 230 criteria in 1988 and 1989. NCHRP 

Report 230 Tests 62 and 63 were conducted on both the Type "C'' dual-post installation 

and the Type "D'' triple-post installation. The dual-post 2.5-pound-per-foot installation 

yielded to the vehicle in both the high- and low-speed tests and allowed it to proceed 

downrange. In the low-speed test of the triple-post installation with two posts impacted. 

the two 3-pound-per-foot diagonal braces that were impacted by the test vehicle yielded 

by breaking from their stubs, but the two signposts subsequently brought the vehicle to a 

controlled stop. In the high-speed test both of the sign posts and diagonal braces 

fractured, allowing the test vehicle to proceed through. The third post that was not 

impacted held the sign in place. Copies of the Test Data Summary Sheets are enclosed for 

reference. Type "C" and "D" refer to the number of u-channcl rails used as lateral braces 

on the back of··A Frame" signs. Type "C" is a single brace while Type •·o" is a dual 

brace as noted on page 2 of 3 of the attached drawings. 
3 

Since NCHRP Report 230 tests 62 and 63 use the same 820-kg test vehicle as specified in 

NCHRP Report 350 and the evaluation criteria are comparable, these tests are considered 

compliant with NCHRP Report 350. The bottom of the signs that span two or three posts 

should be a minimum of 7 feet above the ground. Supplemental signs placed on just one 

of the posts may be mounted at 5 feet above the ground. 

The results of this testing was known to the researchers who conducted a series of sign 

support tests at the FHWA's Federal Outdoor Impact Laboratory in McLean, Virginia, 

from 1989 to 1991. When designing a braced-leg system of u-channel posts they made 

two significant changes to the Minnesota design. The first was to use a breakaway splice 

for the upright sign posts where the signpost overlapped the stub by six inches, with the 

stub projecting no more than 4 inches above the ground. The second innovation was to 

use aluminum fasteners to ease the separation of both the upright and diagonal posts from 

their respective stubs. These changes have the potential for improving the Minnesota 

braced leg design. 

Summary and Standard Provisions 

Therefore, the system described and detailed in the attached form is eligible for 

reimbursement and may be installed under the range of conditions tested. 

Please note the following standard provisions that apply to FHW A eligibility letters: 

• This finding of eligibility does not cover other structural features of the systems, 

nor conformity with the Manual on Uniform Traffic Control Devices. 

• Any changes that may influence system conformance with NCHRP Report 350 

criteria will require a new reimbursement eligibility letter. 

• Should the FHW A discover that the qualification testing was flawed, that inservice performance reveals safety problems, or that the system is significantly 

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

revoke this letter. 

• You are expected to supply potential users with sufficient information on design 

and installation requirements to ensure proper performance. 

• You are expected to certify to potential users that the hardware furnished has the 

same chemistry, mechanical properties, and geometry as that submitted for review, 

and that it will meet the crash test and evaluation criteria of the NCHRP Report 

350. 

• To prevent misunderstanding by others, this letter of eligibility is designated as 

number SS-170 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 letter shall not be construed as authorization or consent by the FHW A to use, 

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

holder. The FHW A does not become involved in issues concerning patent law. 

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

Attachment 
"' 0 

0.000 5 

Test No .•. 

Date ..•. 

Test Article. 

Support • 

Vehicle • Vehicle Weight 

0.398 s 

• 0375-1 

• 05/24/BB 

Sign Installation 

Four, 2.5 lb-ft 

Rerolled Rail U-Post 

Supports 

1979 Honda 

Test Inertia. , •••..• 1,800 lb (817 kg) Gross Static ..•..••• 1,967 lb (892 kg) Vehicle Damage Classification 

TAD •••••••••••• 12FDI 

SAE • • • • • • • • • • • • 12FDLW1 

0.795 s 

Impact Speed. • • . • Change in Velocity •• Change in Momentum. • Vehicle Accelerations 

1.193 s 

19.6 mi/h (31.5 km/h) 13.2 mi/h (21.3 kmVh) 1,084 1 b-s 

(Hax. 0.050-sec Avg) Longitudinal. • • • • -3.18 g Lateral • • • • • • • -1.10 g Occupant Impact Velocity Longitudinal. • • • • 12.89 ft/s (3.93 mfs) Lateral • • • • • • • 4.51 ft/s (1.38 m/s) Occupant Ridedown Accelerations 

Longitudinal. . . . . -2.01 g Lateral . . . . • . . -0.49 g 

Figure 10. Sununary of results for test 0375-l. 
"" w 

0.000 s 

Test No ••• 

Date ••••• 

Test Article. 

Support • 

0.055 s 

. 0375-2 

• 05/24/88 

Stgn Installation 

Four, 2.5 lb-ft 

Rerolled Rail U-Post 

Supports Vehicle • 1979 Honda 

Vehicle Weight Test Inertia •••.•••. 1,800 lb (817 kg) Gross Static •.•••••• 1,967 lb (892 kg) Vehicle Damage Classification 

TAD • • • • • 12FD1 

SAE • • • . . 12FD8Wl 

o.no s 

Impact Speed. . • • . • 

Change in Velocity ••• 

Change tn Momentum ••. 

Vehicle Accelerations 

0.165 s 

61.9 mt/h (99. 7 km/h) 11.5 mt/h (18.4 km/h) 

939 lb-s 

(Max. 0.050-sec Avg) Longitudinal. • • • • -4.04 g Lateral • • • • • • • -2.07 g Occupant Impact Velocity Longitudinal. . • • • 11.70 ft/s (3.57 ~s) 

Lateral • • • . . • . N/A 

Occupant Ridedown Accelerations 

Longitudinal. • . . . -1.18 g Lateral • , • • • • NONE 

Maximum Vehicle crush 

Bumper Height • • 4.0 in (10.2 em) 

Figure · 19. Summary of results for test 0375-2. 
"' 0 

0.000 s 

Test No .•• Date •... Test Article 

Support 

Vehicle. 

Vehicle Weight Test Inertia 

Gross Static . . . . . . . Vehicle Damage Classification 

TAO •••••••••• 

SAE •••••••••• 

0.124 s 0.247 s 

0394·1 Impact Speed •..•• 05/16/89 Change in Velocity •• Minnesota Type Change in Momentum. • •o• Braced Vehicle Accelerations 

Sign Installation (Max. 0.050-sec Avg) 

0.469 s 

. 21,4 mi/b {34.4 km/h) .-11.9 mi/h (19.2 km/h) 

977 lb-s 

• Three 3·lb/ft Longitudinal. . . . . -2.9 g Rerolled Rail Lateral • • • • • • • 1.1 g U·Posts Occupant Impact Velocity 1979 Honda Civic longitudinal •..... 11.0 ft/s (3.3 m/s) Lateral ••...... -6.7 ft/s (2.0 m/s) 

1,800 lb (817 kg) Occupant Ridedown Accelerations 

1,965 lb (891 kg) Longitudinal ...... ·2.3 g Lateral . . . . . . . . 1.2 g 12FDI 

12FDLN1 

Figure 8. Summary of results for test 0394-1. ~~ 
TYPE C & D POST 

RISER POST !NO SPLlC£ PtRWtTT£0) 

2-%;• STAINLESS STEEL OOL TS WITH NYLOH INSERT LOC~ NUTS PLAC£D IN TOP 

M'O eonou HOLtS. 

PANEL 

TYPICAL TYPE C INST ALLA liON TYPICAL TYPE D INST ALLA liON 

U POST SPLICE 

U POST MOUNTING 

TYPE C SIGNS 

MODifiED TYPE C INSTALLATION 

NOTES1 

1- USE J LB/rT STUB POSTS, RISER POSTS, STRINGERS, 

KNEE BRACES, LATERAL BRACES AND KNEE BRACE 

STUB POSTS. ALL SHALL CONf"ORM TO t.IN/DOT 3401. 

2, FOR TYPE D SIGN POSTS LENGTHS AND SPACINGS, 

SEE SIGN DATA SHEET, 

3, TYPE D SIGN PANELS SHALL BE SOL TEO TO STR!NG£RS 

AT 24" MAXIMUM INTERVALS IN ACCORDANCE WITH 

THE TYPE 0 STRINGER AND PANEL-JOINT DETAIL ISEE 

STANDARD SIGNS IIANUAU. 

4. NOUNTING !PUNCH CODE I FOR TYPE C SIGN PANELS 

SHALL BE AS !NO!CATEO IN THI: STANDARD SIGNS MANUAL 

UNLESS OTHERWISE SPEClrtEO. 

5, ALL RISER IVERTICALI U POSTS SHALL BE SPLICED. DRIVEN 

STUB POSTS SHALL BE AT LEAST T' LONG. 

6. USE STAINLESS STEEL ~" BOLTS, WASHERS ANO 

NYLON INSERT LOCK NUTS AS SHOWN FOR All GROUND 

MOUNTED ANO OVERHEAD MOUNTED SIGNS, 

!. STAINLESS STEEL WASHER WITH SAllE DIMENSIONS 

SHALL BE PROVIDED BETWEEN ALL NYLON WASHERS AND 

BOLT HEADS. 

8, BRACING STUBS SHALL BE NO MORE THAN 4" ABOVE 

CROUNO AND EMBEDDED AT LEAST JV,·. 9. A-FRAU( BRACKET SHALL BE STtEL CONf"ORMING TO 

UN/DOT 3306 AND GALVANIZED IN ACCORDANCE WITH 

liN/DOT 3394. 

10, COLLARS SHALL BE USED TO SHIM OVERLAYS AND 

DEMOUNTABLE L(GEIIO AWAY FROM PANEL ftH(RE INTERFER(NCE WITH BOLT HEADS IS ENCOUNTERED. 

UN/DOT 3352.2A5, 

II, 2 POST TYPE C SIGNS SHALL BE REINfORCED WITH 

AT LEAST ONE LATERAL BRACE. INSTALLATIONS WHERE 

THE TOTAL PANEL HCIGHT IS 60" OR MORE SHALL HAVE 

TWO LATERAL BRACES LOCATED APPROXIMATELY AT 

THE QUARTER POINTS, 

12. WHERE 2 SINGLE POST TYPE C SIGNS ARE lNST ALLED 

SlOE BY SIDE, TH(Y SHALL BE REI~'fORCED LATERALLY 

BY AT LEAST 2 BRACES, BOLTED AT EACH POST ANO 

LOCATED APPROXIUATELY AT !HE OUARTER POINTS. 

13. WHERE 3 OR UORE TYPE C SIGNS ARt: INSTALLED 

SIDE BY SIDE, THCY SHALL BE REINrORCEO LATERALLY 

BY AT LEAST 2 BRACES, BOLTED AT EACH POST AND POST 

SECTION AND LOCATED APPROXIMATELY Al THE QUARTER 

POINTS AS SHOWN IN MOOlf!EO TYP( C INSTALLATION. 

TYPE C & D SIGN 

STRUCTURAL DETAILS 

Sheet I of 3 

STATE PROJ. NO. SHEET NO. OF SHEETS 
~ ~ Q 

~ 

~ 

~ s 

0: 

t 

I 

J 

l"' ill !-

~~ ~ <l - ~~~ .. . -.:; ~ .... ~ ... ...... 

~!;~ 

i!S~: 

I 

IJl %;• STAINLESS STEEL BOLTS WITH JJ;- NYLON INSERT LOCK NUTS IN HOLES 

CLOSEST TO SPLICE & OUTSIDE HOLES. 

LATERAL BRACE OR STRINGER 

SPLICE DETAIL <EXPLODED VIEW> 

~· STAIHLESS STEEL· 

BOLTS WITH NYLON 

INSERT LOCK NUTS 

BRAQ((T 

VERTICAL POST 

KNEE BRACE 

SECTION A-A 

11 ·+ l1 3'/:" x 3'/:" SHIU PLATE] 

.......... ·~~:~~:~~~~z .... 

I 

A-FRAME BRACKET 

CST EEL UN/DOT 3306 CAL VAN!ZED PER UN/DOT 33941 

I 

! 

I 

STRINGER 

o/,." STAINLESS STEEL BOLT 

WITH NYLON INSERT LOCK HUT 

SECTION B-B 

!

- o/,." STAINLESS STEEL BOLTS WITH 

NYLON INSERT LOCK HUTS PLACED 

NEAR TOP AND BOTTOU HOLES. 

KNEE BRACE SPLICE 

REVISEDo 1·l-o8 

VERTICAL POST 

- Kll££ BRACE 

CCNE SPLICE 

REOU!R£01 

II 

3.s· 11 

y,·· 

TYPICAL "A-FRAME" INSTALLATION 

TYPE "C" SIGNS 

STATE PROJ. NO. 

TYPICAL "A-FRAME" INSTALLATION 

TYPE "0" SIGNS 

UTC. HT. 

TYPICAL MOUNTING 

Ul OffSET STUB POST 1' TOIIARD ROADWAY 

RELATIVE TO VERTICAL POST. ATTACH STUB 

POST AND KIIEE BRACE BACK TO SACK. 

TYPE C & 0 SIGN 

STRUCTURAL DETAILS 

Sheet 2 of 3 

SHEET NO. OF SHEETS 
a 

~ ::! 

~ § 

~ 

t 

l 

I 

~~ 

!~ 

~~~ ~u .. .-.;; ~ ... ~ ... 1.! .... 

~t~ 

<:!~~ 

I • 

I I 

I I 

I I 

I I 

1.1 t.l 

~ 4 !" l ,·, 

I I I I 

I I I I 

I I l I 

1.1 1.1 I I I --, R6·1. Rl-1 & IR6·3 OR R6·30l 

UOUHTIHG 

~ 

-t+---+----1--+---+- ~ 

REVISEih lG-21-08 

PUNCHING fOR R6·U48" XIS" l 

& Rl-2136" xJ6" xJ6• l 

'i 

1--s·....J.-s .. -l 

-L~ I ~~- 1 I I 

PUNCHING F'OR R6·1136" xl2" l 

6" 

6" 

{ 

i I I I I I £ 

PUHCHIN(; fOR R6·U48" xl8" l 

~ 

iII I I I ~ 

PUNCHING fOR R6-3 OR R6-Jai30" x24"l 

'i r6+6., 

Ef3 I 

'i 

,-

6" +t 

6" 

....L 

c I I I 

-e---e-1 'i I I I 

112-IA (21" xiS" I OR 

IMJ•IA. M3·2A, IIl-JA OR M3·4AI (24" x12"] AND 

111·6 (24" x24"] AND 

f---48"---f 

I f-ta·-+ta--1 I 

r---

t 

---·---< 

PUNCHING F'OR R2·4b 

SP££1) LIMIT 

'i 

1--tz-+ 12"--i 

I I I 

e- -- -e 

I I I 

'i 

T 

12" 

-!-tt. 

6" 

....L 

1M3-lA. M3·2A, 113·3A OR M3·4AJ (30"xl5"1 AND 

t.ll-1 [45"xl6" OR 36"x36"1 

PtlNOIING 

1!.15-IA, 115-2A.116·1A. U6·2A, 116-lA LU;-4A, U6·5A OR t.I6-6Al [21" xJS"l 

PllNCHING 

STATE PROJ. NO. 

I 6·ls"l 

. . 

IWl-1. W1·2, 111·3, Wl·4 OR 111·51& 1113·1 

IIOUNT!NG 

'i 

l-12"+12"--i 

I I c I 

e- -- -e 

I I I 

I I 

'i 

-e- -®-· 

I I T 

12" +'i -

12" 

I I 

-e- -e--l. 

I I 

1113·1. 113-IA, 113·2. M3·2A, 113·3, 113·3A 113·4 OR 

Ml·4AH30" x15"l AND 1111·4 OR MI·SAl 136" x36" I 

PUNCHING 

TYPE C & 0 SIGN 

STRUCTURAL DETAILS 

Sheet 3 of 3 

SHEET NO. OF SHEETS