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Has MwRSF looked into :

1. TL-3 Working widths for various heights of caltrans barrier?

2. A recommendation on what to do near fixed objects (e.g. go with taller barrier, go with vertical barrier, go with taller and vertical barrier) in areas where working width is reduced?

MwRSF has reviewed available information on the working widths and zone-of-intrusion (ZOI) values for the single-slope, concrete barriers evaluated by MwRSF and CALTRANS. Based on this information, the working width and zone-of-intrusion measures for the 32-in. tall, single-slope barrier are approximately 27 and 21 in., respectively. The published ZOI value for the prior TL-3 impacts into 32" tall, sloped-face barriers is 18", while 24" was provided for vertical-face barriers. Actually, the single-slope barrier would likely fall between the two noted ZOI values, thus substantiating the 21" measurement from test no. ZOI-2. The maximum effective height for this lateral extent was nearly 42 in. As such, a conservative approximation would be to use the 27-in. working width value from 32 to 42 in. Beyond the 42-in. barrier height, the ZOI would be approximately zero for TL-3 conditions and valid through the 56-in. barrier height. Thus, the working width for 42 to 56-in. tall, single-slope barriers would be the base barrier width or 24 in.

Please note that these ZOI values provide conservative results for the placement of fixed objects on and nearby the barrier system. Actually, a fixed object could be placed closer to the top-front corner of the barrier as long as acceptable crash performance was obtained.

Previously, MwRSF provided guidance for selecting the top geometry of taller vertical, or near vertical barriers, in an effort to prevent head contact with tall barriers. A head ejection envelope was provided. However, guidance was not provided for sloped-face barriers in terms of the recommended top-barrier geometry or head ejection envelope.

In summary, here are my suggestions:

SS Barrier Height        WW                             ZOI

32"                               27                                21

36"                               27 (assumed)               ?? (measured from top front corner but unknown)

42" (<)                         27 (assumed)               ?? (measured from top front corner but unknown)

42" (>)                         24 (barrier width)        0

51"                              24 (barrier width)        0

56"                              24 (barrier width)        0

Vertical Barrier Height

32"                               24                               24 (vertical barrier has toe and front corner at same position)

In 2023, the National Cooperative Highway Research Program report no. 1018 published recommended envelopes for working widths of barriers for different heights and test levels. In that reserach report, the working width envelopes were described in different lateral and vertical extents of vehicle component intrusion behind a barrier system.

Features which are located in the Zone of Intrusion (ZOI) of rigid barrier systems should be evaluated for crashworthiness. Features located outside of the ZOI may be installed safely without subsequent evaluation according to MASH impact conditions. However, ZOI values are dependent on the impacting vehicle size, shape, weight distribution, and impact conditions. Fixed objects which are outside of the TL-3 ZOI envelopes may still be impacted by single-unit trucks or truck-trailer combination vehicles.

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