May 18, 1999

Refer to: HMHS-B54

Mr. Roberto Fonseca-Martinez

Division Administrator

The Dale Building, Suite 205

1504 Santa Rosa Road

Richmond, Virginia 23229

Dear Mr. Martinez:

On April 2, Mr. Robert McCarty of your staff forwarded a request from Mr. J.G. Browder, Chief

Engineer for the Virginia Department of Transportation, to accept the Modified MB-7D Portable

Concrete Barrier for use on the National Highway System as a test level 3 temporary barrier. 

Included with this request were copies of the Texas Transportation Institute’s January 1999

report, “NCHRP REPORT 350 TEST 3-11 OF THE MODIFIED VIRGINIA DOT PORTABLE

CONCRETE BARRIER,” prepared by Buth, Menges, and Schoeneman, and copies of the crash

test video tape.

The tested barrier was an 810-mm tall F-shaped concrete barrier 6100-mm long. Each segment

was made from 30 Mpa concrete (28 day compressive strength) and contains three longitudinal

#19 bars and one longitudinal #13 bar. Adjacent segments are connected by 25-mm diameter

ASTM A36 steel pins 610-mm long which pass through loops fabricated with 20-mm diameter

steel bars. ASTM F-488 steel washers are used under the pin head and above the 25-mm hex nut

used to retain the pin at the bottom. These and other design details are shown in Enclosure 1.

NCHRP Report 350 Test 3-11 was run on a free-standing installation comprised of five 6100 mm

segments with two 3100-mm long segments added at each end of the test installation, making a

total installation length of approximately 43.3 m. The impact point was 1.3 m upstream from the

joint between segments 2 and 3, or approximately 17 m from the upstream end of the test

installation. Under these conditions, the maximum barrier deflection was 1.83 m. Summary data

from this test are shown in Enclosure 2.

Based on our review of the information you submitted, we have concluded that the tested design

satisfactorily meets the evaluation criteria contained in NCHRP Report 350 for a test level 3

barrier and it may be used on the National Highway System when deemed appropriate by the

contracting agency.

We note that Mr. Browder also requested FHWA acceptance of the State’s method of bolting

temporary concrete barrier to a bridge deck during construction. Unfortunately, there has been

only limited testing of this type of installation to date and we are unable to predict with any

certainty what the outcome of an NCHRP Report 350 test at test level 3 would be. Assuming
2

that field performance of this design has been acceptable, we would agree to its continued use

until such time as it (or a comparable design) is successfully tested, provided such testing takes

place within two years. The State may wish to analyze its bolted design through computer

simulation to gain insight into its likely performance in a full-scale crash test. In this regard, the

FHWA/NHTSA National Crash Analysis Center (NCAC) has developed models that can predict

the performance of portable concrete barriers under impact, including barrier deflection, vehicle

trajectory, and vehicle and barrier loads and accelerations. If the State has an interest in pursuing

this option, the contact person at NCAC is Mr. Azim Eskandarian at (703) 729-8362. Other

questions pertaining to this letter should be addressed to Mr. Richard Powers at (202) 366-1320.

Sincerely yours,

(original signed by Dwight A. Horne)

Dwight A. Horne

Director, Office of Highway Safety Infrastructure

2 Enclosures