The National Highway Traffic Safety Administration (NHTSA) plans to establish a new Federal Motor Vehicle Safety Standard (FMVSS) to require the installation of advanced glazing in buses. The new standard would require impactor testing of glazing material.
The proposed standard, FMVSS No. 217 a, Anti-Ejection Glazing for Bus Portals, would require a 26 kilogram (57 pound) impactor to be propelled from inside a test vehicle toward the window glazing at 21.6 kilometers per hour (13.4 miles per hour).
“The impactor and impact speed would simulate the loading from an average-sized unrestrained adult male impacting a window on the opposite side of a large bus in a rollover,” according to the Federal Register, which published the notice of proposed rulemaking.
“Performance requirements would apply to side and rear windows and to glass panels and windows on the roof to mitigate partial and complete ejection of passengers from these windows and to ensure that emergency exits remain operable after a rollover crash,” according to NHTSA.
The agency also seeks to limit the protrusions of emergency exit latches into emergency exit openings of windows to ensure they do not hinder egress.
The proposed rule would cover high-occupancy buses, generally over-the-road buses of any weight, and non-over-the-road buses with a gross vehicle weight-rating of greater than 11,793 kilograms (26,000 pounds).
“The glazing types currently used in the motor coach industry for side windows are single-pane laminated glass, single-pane tempered (or toughened) glass, or a double-pane of either laminated or tempered glass or a combination of both,” according to NHTSA. “A single-pane laminated glass actually contains two thin glass layers held together by an interlayer, typically of polyvinyl butyral (PVB). The interlayer works to keep the outer layers of glass bonded together in the event they break or crack, and prevents the formation of large shards of sharp glass. Laminated glass may crack or splinter upon impact with the ground, but can still provide a means of keeping passengers within the occupant compartment of the bus if the glazing is retained within the window frame, the PVB interlayer is not excessively torn or punctured, and the window latch remains closed. We believe that laminated glass could meet the requirements proposed in this notice of proposed rulemaking. We consider glass meeting the requirements to be ‘advanced glazing.’”
The estimated cost for the change and testing is $8,700 per bus model.
“We estimate there would be no weight increase due to the proposed requirements; in fact, there could be a weight reduction … as glazing designs change from a double-glazed tempered/tempered configuration to a single-glazed laminated configuration,” NHTSA says.
Comments on the proposed rule are due by July 5, 2016.
To submit a comment or view the proposed rule, click here.