Low-Profile Barrier

In Des Moines, an innovative low-profile barrier was used in the median to shield drivers from the trees as well as light poles and fixed aesthetic features (Figure 108).  The barrier had successfully passed the test-level 2 (45 mi/hr) crash test criteria of NCHRP Report 350.  The barrier terminates with a sloped-down end section where the median narrows adjacent to left-turn lanes (Figure 109).  No trees or other fixed objects were placed in this narrow-median area near intersections.

At a height of only 18 inches, the barrier has a minimal visual impact.  As a mitigation technique, the barrier is expected to reduce crash severities.  It may also have an effect on pedestrian movements, potentially discouraging crossings at unmarked, mid-block locations.  Impacts with the barrier, pedestrian crashes, and speeds are among the variables being monitored in Des Moines as part of the in-service evaluation.

FIGURE 108 A low-profile barrier was used along the median of SR 99 in Des Moines.

Figure 108 is a photo showing a low-profile concrete barrier, approximately 20 inches in height, surrounding the median and shielding drivers from the trees and light poles in the median and the opposing traffic.

FIGURE 109 Sloped-down end section adjacent to turn lane.

Figure 109 is a photo showing the low-profile barrier described for Exhibit 7.13 as it slopes down to the curb elevation at a left-turn lane.

FIGURE 110   Two low-profile concrete barriers have passed NCHRP Report 350 test-level 2 (45 mi/hr) crash testing.

Figure 110 consists of two photos showing two types of low-profile concrete barriers.  In the top photo, the face of the barrier adjacent to traffic projects outward near the top.  In the bottom photo, the barrier shape tapers outward slightly from bottom to top.
 
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