Movement of 14-foot-wide Manufactured Housing Units with the Roof Eaves of 1 Foot or Less

About the report:

This study was carried out in response to a request from the Virginia Manufactured Housing Association to be allowed by blanket permit to ship homes 14 feet wide at the base with roof eaves of up to 1 additional foot. In Virginia, the current maximum width allowed to be shipped under a blanket permit is 14 feet. This two-part study included (1) a survey of the policies and practices of other states, and (2) an analysis of centerline and edgeline encroachment data obtained by videotaping test runs of one standard 14-foot-wide control unit and three 14-foot-wide experimental units with different I-foot roof-eave configurations made available by the industry. Forty-two states replied to the survey: 34 reported that movement of housing units more than 14 feet wide is permitted, and 23 reported that movement of units 16 feet wide, or wider, is permitted. The pilot study identified four measures of risk to other travelers. From greatest to least potential risk, they were (1) wheels over the centerline, (2) side over the centerline, (3) wheels over the edgeline, and (4) side over the edgeline. The encroachment data were analyzed by total trip and by trip segment, which was based on the number of lanes of travel. The portions of the total trip with two and three lanes of travel are equivalent to roads that require a single-trip permit, and the portions with four or more lanes are equivalent to most roads in the blanket permit network. It was found that both for the total trip and for segments with four or more lanes of travel, the experimental units did not have more encroachment than the control unit for three measures of risk (wheels over centerline, side over centerline, and wheels over edgeline). Although the experimental units had statistically more encroachment than the control unit for the fourth measure (side over edgeline), most of the encroachment was on the four-lane divided segments and the actual differences were relatively small (less than 4% of the trip). The experimental units had more encroachment of the centerline (wheels and side) than the control on segments with two or three lanes but not more encroachment of the edgeline (wheels and side). It was concluded that 14-foot-wide housing units with roof eaves up to 1 additional foot would create minimal additional safety risk to other motorists on roads with four or more lanes but have the potential to impose additional safety risks on roads with two or three lanes. It is recommended that VDOT allow the industry to move 14-foot-wide housing units with roof eaves up to 1 foot on the blanket permit network. It is also recommended that the industry be required to maintain data on crashes, vehicle miles of travel (exposure), and route movements of these wider loads and furnish it to VDOT upon request. In addition, it is recommended that VDOT carefully evaluate requests to move these units on roads with two or three lanes to ensure there is sufficient roadway width and roadside clearance for a safe move. Finally, it is recommended that VDOT encourage AASHTO to undertake through the National Cooperative Highway Research Program a national study of all types of wide load movements so that uniform standards can be established for use by all states.

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