The automotive industry is witnessing a growing trend towards the use of laminated glass in side and rear windows of vehicles. While this shift is driven by new safety standards aimed at reducing ejection injuries in crashes, it may have unintended consequences for occupant rescue and escape in submerged vehicle incidents. As more vehicles adopt laminated glass, there are concerns that they could become “glass coffins” in water, making it harder for occupants to exit or be rescued.
Laminated glass, which consists of two or more glass layers bonded together with a plastic interlayer, has long been used in vehicle windshields for its safety benefits. In recent years, however, its use has been expanding to side windows as well. In 2021, around 25-30% of all vehicles sold in North America already had laminated sidelites on the front doors [1]. Some European automakers like Mercedes and BMW are standardizing side glazing in their top-selling models [2].
Looking forward, the laminated glass segment is anticipated to witness rapid growth at a compound annual growth rate (CAGR) of 7.3% in coming years [3]. The passenger cars segment, which primarily utilizes laminated glass for safety, captured approximately 67% revenue share of the automotive glass market in 2022 [4]. If current trends continue, it is plausible that 40-50% or more of new vehicles sold could have laminated side glass by 2030 [1][2][4].
This shift towards laminated glass is largely driven by the introduction of (US) Federal Motor Vehicle Safety Standard 226 (FMVSS 226) for ejection mitigation. Aimed at preventing occupant ejection through side windows in a crash, FMVSS 226 has made laminated glass a key countermeasure for compliance [5].
The standard was introduced to address the high fatality risk associated with ejection. In rollover crashes, the ejection fatality rate is over 4 times higher for unrestrained occupants [6]. Side window ejections account for 62% of all fatal occupant ejections in crashes [7]. Seatbelt use was found to virtually eliminate the risk of complete ejection, but for unbelted occupants, the risk is significantly increased [8].
While FMVSS 226 may reduce ejection injuries and fatalities, it does not address the issue of vehicle submersion and occupant drowning. Drowning is a leading cause of vehicle-related fatalities, with some studies finding vehicle-related incidents accounting for up to 63% of flood deaths [9].
The use of laminated glass in side windows can make escape or rescue from a submerged vehicle significantly more difficult, as the glass cannot be easily broken. This raises the question – why has ejection mitigation been prioritized over drowning prevention in vehicle safety standards? Especially when considering that increased seatbelt use is a highly effective ejection countermeasure, with only 1% of ejected occupants wearing a seatbelt compared to over 30% of non-ejected occupants [10].
As more vehicles adopt laminated glass to meet FMVSS 226, there is a growing need for drowning prevention measures. One promising solution is the Automatic Window Opening System (AWOS) developed by AWOS Tech [11]. This system can detect when a vehicle is submerged and automatically open the electric windows to allow escape. Such systems could be a lifesaving feature if widely adopted by vehicle manufacturers.
Estimates of total flood fatalities in the U.S. range from 60-100 deaths per year on average [12]. While exact numbers for vehicle-related drownings are not always specified, applying the 63% proportion from some studies would estimate around 38-63 annual vehicle-related flood deaths [9][12]. More research is needed to determine precise averages, but the available data suggests vehicle-related drownings account for a significant portion of flood fatalities.
Even if there are changes to standards at some point in the future, the challenge for first responders to gain access through laminated glass is an issue and will continue as a legacy problem for some time. What we do know is the centre-punch and hammer type window breaking tools (i.e. Res-Q-Me) are not effective in breaching laminated glass [13]. Though there are tools to slide down to derail side windows from their internal mounting, once windows are up and water force laterally applied, they are difficult to impossible to be lowered. Though further research is needed in the context of effectiveness in shallow water, existing tools such as the Glas-Master (manual saw), Nemo waterproof reciprocating saw (battery powered), Halmatro T1 Forcible Entry Tool and BreachPen (thermal cutting wand) could be viable options for use in swiftwater.
Based on the available data, there is a concerning trend of increasing obesity rates among adults in the United States, which may have implications for vehicle safety in emergency situations. According to the CDC, the prevalence of obesity among U.S. adults has risen significantly over the past few decades, with 42.4% of adults classified as obese in 2017-2018 [14][15]. This increase in obesity rates could potentially make it more difficult for some individuals to exit a vehicle through windows in emergency scenarios.
While there are no specific studies directly examining the relationship between obesity and emergency vehicle egress, research has shown that obesity can affect mobility and physical capabilities [16]. As body size and weight increase, manoeuvring through confined spaces like vehicle windows may become more challenging. Additionally, studies on vehicle occupant safety have noted that obesity can impact interactions with vehicle restraints and overall kinematics during collisions [16].
With hydrostatic pressure making opening of doors and windows difficult to impossible once a vehicle is fully submerged [17], even with automatic window opening systems, it is likely that some occupants due to disability, obesity or pregnancy may not be able to easily exit through side windows. This leaves the rear window of vehicles as the only option to escape or be rescued through. Vehicle safety standards should consider a means for the jettison of the rear window through an internal pull-tab that is illuminated when vehicle submergence is detected, and after the side windows are lowered to indicate a final exit option.
It is not common to use bariatric victims during swiftwater vehicle rescue training, though these are more likely to be vulnerable in such incidents. Such incidences may require breaching the rear window, lowering the back rest to the horizontal position and extricating the victim by pulling them out flat by their shoulders. In-water vehicle rescue props should accommodate teaching this method.
In conclusion, while laminated glass offers important safety benefits in crashes, its growing use in vehicles also creates new challenges for occupant escape and rescue in submersion incidents. As we strive to reduce ejection fatalities, we must not neglect the significant risk of drowning in vehicles.
Innovative safety features like automatic window opening systems may help mitigate this risk and prevent vehicles from becoming “glass coffins” in water. Ultimately, a comprehensive approach that addresses both ejection and submersion dangers is needed to maximize occupant protection. By raising awareness of this issue among automakers, policymakers, and the public, we can work towards solutions that will save lives on and off the road.
[1] https://www.marketsandmarkets.com/Market-Reports/automotive-glass-market-229009655.html
[2] https://www.linkedin.com/pulse/laminated-glass-automotive-market-research-report-2031-9kpfe/
[3] https://www.precedenceresearch.com/automotive-glass-market
[4] https://www.linkedin.com/pulse/automotive-window-laminated-glass-market-research-report-iwpze/
[5] https://www.nhtsa.gov/sites/nhtsa.gov/files/tp-226_ejection_v00_march_2011.pdf
[6] https://www.lthlaw.com/2022/07/occupant-ejection/
[7] https://www.semanticscholar.org/paper/6608382f25c6bdca198d3ecfa9a6733cae4b4c7e
[8] https://pubmed.ncbi.nlm.nih.gov/23169130/
[9] https://repository.library.noaa.gov/view/noaa/32322/noaa_32322_DS1.pdf
[10] https://www.edgarsnyder.com/resources/seat-belt-statistics
[11] https://www.awostech.com/
[12] https://www.researchgate.net/figure/Monthly-distribution-of-vehicle-related-flood-fatalities-and-average-monthly_fig1_346299167
[13] https://www.aaa.com/AAA/common/AAR/files/Research-Report-Vehicle-Escape-Tools.pdf
[14] https://www.niddk.nih.gov/health-information/health-statistics/overweight-obesity
[15] https://www.cdc.gov/nchs/fastats/obesity-overweight.htm
[16] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3256798/
[17] [https://www.researchgate.net/publication/45492713_My_Car_Is_Sinking_Automobile_Submersion_Lessons_in_Vehicle_Escape
