Senator Teresa Manzella, sponsor of Senate Bill 433, told the House Transportation Committee she brought the measure to “codify our behavior and our expectations of handling, driving through a roundabout,” specifically to address how tow vehicles pulling trailers should be treated.

The bill would add a new section to state code saying that when a tow vehicle and another vehicle enter a roundabout simultaneously, the vehicle towing a trailer would be given the benefit of the doubt and other vehicles “must yield the right of way and may not attempt to pass.” That language appears in line 20 of the draft provided to the committee.

The measure’s sponsor said the proposal grew from local disputes and safety concerns in the Bitterroot Valley and at a proposed Bell Crossing site, and she gave examples involving horse trailers and liquid loads that can shift when a towing vehicle’s rear wheels do not track the same path as the towing vehicle’s front wheels.

Larry Flynn, deputy director for the Montana Department of Transportation, testified in support and called the bill “a good common sense approach to help improve the safety of an already safe tool that we have.” Flynn said giving constrained tow vehicles a statutory right of way would improve safety and functionality of roundabouts.

Dustin Ross, chief engineer for the Montana Department of Transportation, told the committee the department reviewed laws across the United States and found three other states that have enacted similar legislation; he also said the Manual on Uniform Traffic Control Devices committee is considering signage for multi-lane roundabouts to indicate yielding to trucks. "To our knowledge, there are 3 other states that have enacted legislation," Ross said.

Committee members asked for additional information and asked the Montana Department of Transportation to supply crash-history data comparing severe injuries and fatalities at roundabouts with traditional intersections. Ross responded the department tracks before-and-after crash histories for roundabouts and can provide that information.

Members also raised operational concerns: backups at specific roundabouts, motorists entering and going the wrong way, oversized loads that traverse roundabouts in the opposite direction by design, and snowplow clearance. DOT staff said they would investigate specific problem locations and noted that very large loads are sometimes routed through roundabouts in reverse with pilot vehicles to protect other drivers.

Senator Manzella pointed to a clause in the bill that would allow a tow vehicle, "with due regard for all other traffic, [to] deviate from its lane in order to safely approach or pass on the roundabout island," and she asked the committee for a do-pass recommendation.

The committee closed the hearing on Senate Bill 433 without recording a committee vote. No opponents testified in person or online during the hearing.

The committee requested follow-up information from the Department of Transportation on crash data and signage options; the department agreed to provide the requested crash history and to look into the specific roundabout locations raised during questions.