Refer to: HSA-10/WZ-133

Mr. Ron Faller 

Midwest Roadside Safety Facility 

1901 “Y” Street, Bldg. C 

P.O. Box 880601 

Lincoln, Nebraska 68588-0601 

Dear Dr. Faller: 

Thank you for your September 12, 2002, letter requesting Federal Highway Administration 

(FHWA) acceptance of the Minnesota Department of Transportation (DOT) temporary work 

zone sign stand as a crashworthy traffic control device for use in work zones on the National 

Highway System (NHS). Accompanying your letter was a report of crash testing you conducted 

and a CD of the tests. You requested that we find these devices 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.” 

Introduction 

The FHWA guidance on crash testing of work zone traffic control devices is contained in two 

memoranda. The first, dated July 25, 1997, titled “INFORMATION: Identifying Acceptable 

Highway Safety Features”, established four categories of work zone devices: Category I devices 

were those lightweight devices which could be self-certified by the vendor, Category II devices 

were other lightweight devices which needed individual crash testing, Category III devices were 

barriers and other fixed or massive devices also needing crash testing, and Category IV devices 

were trailer mounted lighted signs, arrow panels, etc. The second guidance memorandum was 

issued on August 28, 1998, and is titled AINFORMATION: Crash Tested Work Zone Traffic 

Control Devices.” This later memorandum lists devices that are acceptable under Categories I, 

II, and III. 

A description of the device follows: 

The Minnesota DOT rigid panel portable sign support is a stiffened perforated square steel tube 

“H-Footprint” device: 

• Vertical upright masts are 44.5 mm (1.75 inch) square galvanized Telespar ASTM A-653 

Grade 50 steel tubing with 2.67 mm (0.105 inch) wall thickness and a length of 1524 mm 

(60 inches.) 

• Outside vertical upright tubing is 50.8 mm (2 inch) square galvanized Telespar ASTM 

A-653 Grade 50 steel tubing with 2.74 mm (0.108 inch) wall thickness and a length of 

911 mm (33.875 inches.) 
2

• Horizontal legs are 38.1 mm (1.5 inch) square galvanized Telespar ASTM A-653 Grade 

50 steel tubing with 2.74 mm (0.108 inch) wall thickness and a length of 1524 mm 

(60 inches.) 

• Vertical stubs from the legs are 38.1 mm (1.5 inch) square galvanized Telespar ASTM 

A-653 Grade 50 steel tubing with 2.74 mm (0.108 inch) wall thickness and a length 

305 mm (12 inches.) It is welded to the horizontal leg on all four sides. 

• The outside vertical upright tubes slide over the vertical uprights and the vertical portion 

of the legs slide into the vertical upright masts with 7.9 mm (0.3125 inch) diameter x 

63.5 mm (2.5 inch) long hex head S30400 threaded bolts used to fasten the masts and 

legs. 

• The solid, 2.74 mm (0.108 inch) aluminum sign panel was 1219 mm (48 inch) diamond 

shaped and fastened to the stand with four 7.9 mm (0.3125 inch) x 63.5 mm (2.5 inch) 

long hex head S30400 threaded bolts. 

• Height to bottom of sign: 335 mm (13.1875 inches) Height to top of outer tube 959 mm 

(37.74 inches). Height to the Warning Light bolt, 1,481 mm (58.3125 inches). 

• The legs have a mass of 9.1 kg (10 pounds) and the panel, masts, outside tubes, and light 

have a mass of 36.75 lg (81 pounds.) One 20 kg (45 pound) sandbag was placed at the 

end of each leg. 

Testing 

This crash-testing program used a hard-nosed bogie vehicle of a mass larger than the standard 

820C test vehicle. There are significant constraints involved in using such a non-standard testing 

device, some of which are: 

1. The potential vehicle velocity change must be considered insignificant. 

2. The crush characteristics of an automobile bumper must not be expected to have a 

significant affect on the trajectory of the test article. 

3. The profile of the bogie vehicle must be configured to replicate the outline of a 

production vehicle. The MWRSF bogie was configured to replicate the outline of a Geo 

Metro, a vehicle commonly used in testing of work zone devices. 

4. No part of the test article may intrude into the windshield area of the vehicle after impact. 

The two tests and their results summarized below were within these constraints. 

Stand-alone examples of the devices were tested in separate tests, one head-on and one turned at 

90 degrees, as called for in our guidance memoranda. The complete device, as tested is shown in 

Enclosure 1. The crash test is summarized in the table below: 

Test Number MNSB-12 MNSB-13 

Test Article Head-on End-On 

Flags or lights One lightweight warning light on each stand 

Test Article Mass (each) 45.8 kg (91 pounds) plus ballast 

Bogie Inertial Mass 974 kg (2148 pounds) 
3

Impact Speed 97.5 km/hr (60.6 mph) 98.8 km/hr (61.4 mph) 

Approx. Velocity Change 10 km/hr, 2.78 m/s 10 km/hr, 2.78 m/s 

Findings 

The rigid frame of these stands caused them to be pushed ahead of the bogie, or knocked to one 

side. Neither showed any potential for approaching the windshield or causing any other 

passenger compartment intrusion. The trajectory of the sign stands in these tests indicate that the 

bogie vehicle, even though it was not within the specification range of an NCHRP Report 350 

820C test vehicle, was acceptable for establishing the crashworthiness of the stands. The results 

of the testing met the FHWA requirements and, therefore, the devices described above and 

shown in the enclosed drawings for reference are acceptable for use on the NHS under the range 

of conditions tested, when proposed by a State. 

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

! Our acceptance is limited to the crashworthiness characteristics of the devices 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 device 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 device being marketed is 

significantly different from the version that was crash tested, it reserves the right to 

modify or revoke its 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 they will meet the crashworthiness 

requirements of FHWA and NCHRP Report 350. 

! To prevent misunderstanding by others, this letter of acceptance, designated as 

number WZ-133 shall not be reproduced except in full. This letter, and the test 

documentation upon which this letter is based, is public information. All such 

letters and documentation may be reviewed at our office upon request. 

Sincerely yours, 

Carol H. Jacoby, P.E. 

 Director, Office of Safety Design 

Enclosure