December 18, 2002

Refer to: HSA-10/WZ-130

Mr. David Stoudt
Sign Up Corporation
P.O. Box 14624
Portland, Oregon  97293

Dear Mr. Stoudt:

Thank you for your letter of June 14, 2002, requesting Federal Highway Administration (FHWA) acceptance of your company=s X-CELL 48 HDL tall portable sign stands as crashworthy traffic control devices for use in work zones on the National Highway System (NHS).  Accompanying your letter was a report of crash testing conducted by E-Tech Testing Services and a video 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.”  You provided additional information at our request via a facsimile message on December 12, 2002.


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 brief description of the devices follows:

The X-CELL 48 HDL Sign Stand is a portable sign system featuring a spring loaded upright support and a 1219 mm x 2 mm thick diamond shaped aluminum sign. The sign stand has four legs made of 25.4 mm square 2 mm wall tubing. The tips of the legs are rubber capped and form a 2235 mm by 1321 mm base pattern. The material specification is ASTM A500/A513 Grade A for all ERW (electronic resistance welded) steel square tubing used in the sign support.  Each leg is attached to an “X-CELL” assembly which spring loads the sign support upright.

The X-CELL assembly in turn supports a sign mounting stem “socket” made from 31.8 mm square 2.4 mm wall tube.  A 25.4 mm square 2 mm wall steel tubing “center mast” is locked into the stem by a spring detent pin.  A 19.1 mm square 1.6 mm wall steel tubing “upper mast” is locked into the stem by a spring detent pin.  The sign is mounted to the mast with two sliding “rigid sign clamps.”  Each clamp has two 9.5 mm carriage bolts with wing nuts used to clamp down on the sign corner.  The clamps are secured in position on the mast with a thumbscrew.  The lower rigid sign clamp supports the bottom of the sign 1626 mm above ground level.  A flag holder, made of two 20 gage steel plates formed and spot welded together, completes the top of the mast.  Three 457 mm square vinyl fabric flags with wooden dowels were attached to the top of the support.


Full-scale automobile testing was conducted on your company=s devices.  Two stand-alone examples of the device were tested in tandem, one head-on and the next placed six meters downstream 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


Test Article

X-CELL 48 HDL Sign Stand with 2 mm Aluminum Sign

Height to Bottom of Sign

1626 mm

Height to Top of Sign

3350 mm

Flags or lights

Three flags on wood dowels

Test Article Mass (each)

28.1 kg, ballasted with four 16 kg sand bags

Vehicle Inertial Mass

820 kg

Impact Speed, Head-on

101.1 km/hr

Impact Speed, 90 Deg.

97.5 km/hr

Velocity Change, Head-on

1.00 m/s

Velocity Change, 90 deg.

1.00 m/s

Vehicle crush

None, slight cosmetic damage only

Occupant Compart. Intrusion


Windshield Damage

No contact by sign nor stand


Damage was nonexistent in this impact as the mast separated from the base and the sign rotated over the vehicle in both impacts.  Velocity changes were well below the maximum and within the “desirable” range.  The results of the testing met the FHWA requirements and, therefore, the portable sign stand 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:

Sincerely yours,

Harry W. Taylor
Acting Director, Office of Safety Design