Current TxDOT practice allows installation of all existing chevron sizes on 7-ft mounting height, but restricts the use of 4-ft mounting height for the three smallest existing chevron signs--that is, 12 inches x 18 inches, 18 inches x 24 inches, and 24 inches x 30 inches. A common TxDOT practice is to install chevron sign systems in roadside ditches. For this type of installation, the specified sign mounting height is measured from the pavement surface. When a sign support system is installed on a slope, the local mounting height of the sign (calculated from ground level at the location of installation) will be greater than the same mounting height evaluated for the same sign installed on flat level ground. Previous crash testing was performed with the chevron installed on flat, level ground. Since it is common practice for TxDOT to install chevron signs in ditches at a 4-ft mounting height and a lateral offset between 2 and 8 ft from the pavement surface, the actual ground mounting height varies. TxDOT research project 0-6363 suggested the crashworthiness of this configuration be evaluated. The scope of this study was to evaluate the impact performance of a 24-inch x 30-inch chevron sign at a 4-ft mounting height from the pavement surface, installed at an 8-ft lateral offset in a 5.5H:1V sloped ditch. The chevron sign support performed acceptably for MASH Test 3-61 (1100C vehicle impacting at 62 mi/h and 10 degree nominal conditions). Thus, the current TxDOT practice of installing the three smallest chevron signs (12 inches x 18 inches, 18 inches x 24 inches, and 24 inches x 30 inches) at 4-ft mounting height in roadside ditches is acceptable.
展开▼
