Road departure mitigation system (RDMS), a vehicle active safety feature, uses road edge objects to determine potential road departure. In the U.S., 45%, 16%, and 15% of car-mile (traffic flow * miles) roads have grass, metal guardrail, and concrete divider as road edge, respectively. It is difficult to test RDMS with real roadside objects. Lightweight and crashable surrogate roadside objects that have representative radar, LIDAR and camera characteristics of real objects have been developed for testing. This paper describes the identification of automotive radar, LIDAR, and visual characteristics of metal guardrail, concrete divider, and grass. These characteristics will be referenced for designing and fabricating the representative surrogate objects for RDMS testing. Colors and types of the roadside objects were identified from 24,735 randomly sampled locations in the US using Google street view images. The radar and LIDAR parameters were measured using 24GHz/77GHz radar and 350-2500nm IR spectrometer.

Metal guardrail:​ The peak 24GHz RCS (Radar Cross Section) of W-beam and I-beam of guardrail are 10dB and 13dB. The peak 77GHz RCS for W and I-beam are 15dB and 20dB. When the radar beam direction is not perpendicular to the metal guardrail surface, the reflectivity decreases significantly. As the illumination/measurement angle increases from 0 to 70 o , the IR reflectance of metal guardrail decreases from 1.3 to 0.1, and the variation among samples decreases from 1.5 to 0.05. The age of the metal guardrail does not affect the RCS if steel rust is not present.

Concrete divider:​ Both 24GHz and 77GHz radar reflectivity are -7.3dB. The age of the concrete divider does not affect the radar reflectivity, but the surface smoothness and material affect the reflectivity. As the illumination/measurement angle increases from 0 to 70 o , the IR (Infrared) reflectance of concrete divider increases by only 0.1.

Grass:​ The peak 77GHz RCS is -18dB at 10 o depression angle. Different kinds of grass (wild vs. maintained, short vs. long, even vs. uneven) have similar RCS value when measured under the same conditions (same radar type, same polarization, and same pitch angle. Same grass field will produce different RCS during different seasons or after rain where the moisture content of grass produces different reflectivity. As the illumination/measurement angle increases from 0 to 70 o , the IR reflectance of grass increases from 0.1 to 1 and the variation among samples increases from 0.2 to 1. The most representative grass road-edge is uneven yellow/green mixed short grass followed by even green and short grass. 18 most occurring grass color patterns were selected.