## fixed object density

Safety performance functions, development (calibration, crash modification factors [Part C], crash proportions), IHSDM and other software

Moderator: khardy

### fixed object density

Is a bridge a fixed object? How to determine its density if there is one per a segment which is 0.1 mile long? What about guiardrails and barriers? The same question about density.
Any publication on fixed objects types and density?
elenabrunstein

Posts: 3
Joined: Wed Sep 12, 2012 3:00 pm

### Re: fixed object density

Here is a reply sent to me by Mike Dimaiuta

You are correct that HSM Ch. 12 does not provide detailed guidance regarding bridges, specific barrier types or guardrail. It is unclear to me whether a bridge (bridge rails) or guardrail would be considered roadside fixed objects. The HSM (p. 12-41) states that, “In estimating the density of fixed objects, only point objects that are 4 inches or more in diameter and do not have breakaway design are considered.” The HSM (p. 12-41) also states that “Continuous objects that are not behind point objects are counted as one point object for each 70 ft of length.” So, in the case of a continuous barrier, divide the length of the barrier by 70 ft. For example, a 280 ft long wall would be considered as 280/70 = 4 point objects.

For sites/segments less than 1 mile long, take the number of fixed objects divided by the length of the site to get the density. For example, if a 0.1 mi segment has 3 fixed objects, then the fixed object density would be 3 fixed objects/0.1 mi = 30 fixed objects/mi.
elenabrunstein

Posts: 3
Joined: Wed Sep 12, 2012 3:00 pm