Safety Glass: A Mandatory Law And Its History

Safety glass, which is designed to be less likely to break and less likely to pose a threat when broken, has been a legal requirement in the United States since the 1960s. The Highway Safety Act of 1966 was the first piece of legislation that gave the government the authority to set safety standards for cars, including shatter-resistant windshields. However, the history of safety glass goes back much further, with the invention of laminated glass by French chemist Édouard Bénédictus in 1903. Today, safety glass is required by law in various applications, including automotive windshields and building codes, to protect people from injury in the event of accidents or glass breakage.

Laminated glass in vehicles

The use of safety glass in vehicles has evolved over the years, with advancements in technology leading to the development of laminated glass and tempered glass. Laminated glass, the focus of this discussion, has become a crucial component in enhancing safety and improving the overall driving experience.

The Invention of Laminated Glass

Laminated glass was invented in the early 20th century by French chemist Édouard Bénédictus. The serendipitous discovery occurred when Bénédictus accidentally dropped a glass flask coated with cellulose nitrate, noticing that it cracked but did not shatter. This led to further experimentation and the creation of laminated glass, which played a significant role in revolutionising automotive safety.

Laminated glass is composed of multiple layers of glass bonded with a plastic interlayer, typically polyvinyl butyral (PVB). This interlayer gives laminated glass its unique properties, allowing it to absorb impact and remain intact. In the event of a collision, laminated glass significantly reduces the risk of injuries from flying glass. The adoption of laminated glass in vehicle manufacturing prioritises passenger safety and sets a benchmark for automotive design.

Benefits of Laminated Glass in Vehicles

Laminated glass offers several advantages over traditional glass in vehicles. Firstly, it provides enhanced safety by remaining intact during accidents, reducing the likelihood of occupants being ejected from the vehicle. This feature complies with the Ejection Mitigation rule passed by the National Highway Traffic Safety Administration (NHTSA) in 2011, which aims to keep occupants inside the car during a rollover. Additionally, laminated glass reduces outside noise, creating a quieter and more comfortable cabin. The interlayer also blocks a significant amount of UV radiation, protecting occupants from harmful rays.

Drawbacks of Laminated Glass in Vehicles

While laminated glass offers improved safety and noise reduction, it also presents some challenges. One notable drawback is the difficulty in breaking laminated glass in emergency situations. Traditional glass-break tools are ineffective against laminated glass, and even first responders may have difficulty breaking through with specialised tools. This can pose a problem if occupants need to escape from a sinking or burning vehicle. However, the likelihood of such emergencies is extremely low, and laminated glass is more likely to reduce injuries and save lives in the vast majority of accidents.

Safety glass in buildings

Safety glass is a type of glass that has additional safety features, making it less likely to break and less likely to pose a threat when broken. It is commonly used in buildings to enhance safety and protect occupants from injury. The history of safety glass in buildings dates back several decades, with advancements and regulations contributing to its widespread adoption.

Types of Safety Glass

There are three main types of safety glass: toughened glass (tempered glass), laminated glass, and wire mesh glass (wired glass). Each type employs distinct techniques to improve safety:

• Toughened glass is created through controlled thermal or chemical treatments, increasing its strength compared to normal glass. When broken, it crumbles into small granular chunks instead of splintering into jagged shards, reducing the risk of injury.
• Laminated glass is composed of layers of glass and plastic held together by an interlayer, typically polyvinyl butyral (PVB). When broken, the interlayer keeps the layers bonded, and the glass crumbles into small pieces, preventing large sharp fragments.
• Wire mesh glass incorporates a grid or mesh of thin metal wire embedded within the glass. While it is weaker than unwired glass, it is used for its fire-resistant abilities and ability to remain in the frame even when cracked under thermal stress.

Safety Glass Regulations

The use of safety glass in buildings is often mandated by regulations and building codes to ensure properties are safer. Here are some notable regulations and their impacts:

• The Highway Safety Act of 1966 in the United States was the first legislation granting the government authority to set safety standards for cars, making shatter-resistant windshields mandatory.
• Since 1977, Federal law in the United States has required safety glass in doors and tub and shower enclosures.
• The International Residential Code (IRC), in effect since 2000, includes safety glass requirements.
• The Florida Building Code (FBC) and Uniform Building Code (UBC) have incorporated safety glass regulations since their inception.
• The Consumer Products Safety Council (CPSC) established federal regulations known as "CPSC 16 CFR 1201," which came into effect on July 6, 1977.

Applications of Safety Glass in Buildings

Safety glass is typically required in areas where there is a potential for human impact with the glass. Some common applications include:

• Skylights
• Exterior storefronts, curtain walls, and windows in geographical areas requiring hurricane-resistant construction
• Doors, shower doors, and tub enclosures
• Low windows in walking areas
• Architectural glass doors and tables
• Refrigerator trays

The use of safety glass in these areas helps prevent injuries and enhances the overall safety of building occupants.

The Highway Safety Act of 1966

The Act was proposed by President Lyndon B. Johnson in his 1966 State of the Union Address, alongside the formation of a new executive agency, the Department of Transportation. It was strongly supported by Public Works Chairman George Fallon of Maryland, who stated that the bill:

> continues the policy of meaningful cooperation between the States and the Federal Government on highway matters. I believe it is a firm step forward in the struggle to save lives, and I urge that we act with a strong voice to put it into effect.

The Act addressed a broad range of issues, including driver education, licensing, pedestrian performance, vehicle registration and inspection, traffic control, highway design and maintenance, accident prevention, investigation, and record-keeping, and emergency services. It mandated that each state must "have a highway safety program approved by the [Secretary of Commerce]... in accordance with uniform standards to be approved by the Secretary."

Congress authorized funds for distribution to the states, with a requirement that each state implement a highway safety program by December 31, 1968, or lose 10% of their apportioned funds. The Highway Safety Act of 1966 enjoyed strong bipartisan support and passed the House by a vote of 318-3. It was signed into law by President Johnson on September 9, 1966.

The role of safety glass in preventing ejection during collisions

Safety glass is a legal requirement in many developed countries, where it is included in building regulations to ensure properties are safer. In the context of automobiles, safety glass plays a critical role in preventing ejection during collisions.

The first windshields, introduced in 1904, were made of the same material as house windows and were prone to shattering, creating dangerous shards that posed significant risks to passengers. The development of safety glass, or laminated glass, revolutionized automotive safety. Laminated glass, composed of two layers of glass bonded with a plastic interlayer, was invented in 1903 by French chemist Édouard Bénédictus. This type of glass can absorb impact and remain intact, significantly reducing the risk of injuries from flying glass in accidents.

The benefits of laminated glass in preventing ejection during collisions are significant. When laminated glass breaks, the interlayer holds the pieces of glass together, creating a "spider web" cracking pattern. This prevents the glass from shattering and provides a barrier that keeps occupants inside the vehicle. This is especially important in rollover accidents, where the physical characteristics of the collision can force the head, upper torso, and arms of a passenger out of the protected area, even if they are wearing a seatbelt.

The effectiveness of laminated glass in preventing ejection is well-documented. Studies have shown that a person partially or totally ejected from a vehicle during an accident is ten times more likely to die than someone who remains inside. Between 700 and 1,000 people suffer serious injuries each year due to partial ejection, and about 36,000 vehicle occupants are ejected annually. The use of laminated safety glass has been found to significantly reduce the risk and occurrence of ejection for both belted and unbelted passengers.

Despite the proven benefits of laminated glass, automobile manufacturers have not consistently utilized it in all windows. While it is mandatory for windshields in many countries, including the United States, it is not required for other windows. Beginning in the late 1950s and early 1960s, manufacturers opted for cheaper tempered glass for passenger windows. This decision has been criticized by safety experts, who argue that tempered glass shatters into thousands of tiny, sharp pieces during accidents, providing little barrier to ejection.

In recent years, some carmakers have acknowledged the shortcomings of tempered glass, with a few conceding that it offers no safety benefits. BMW has become the first manufacturer to offer laminated safety glass as an option for all vehicle windows, although it comes at an additional cost to consumers.

In conclusion, the role of safety glass in preventing ejection during collisions is crucial. Laminated glass provides a strong barrier that keeps occupants inside the vehicle, reducing the risk of serious injury and death. While it has been standard equipment for windshields since the 1930s, its use in other windows has been limited due to cost considerations. However, with growing awareness of the benefits of laminated glass, there may be a shift towards its wider adoption in the automotive industry.

The invention of safety glass

Intrigued by this observation, Benedictus began experimenting with coating glass in liquid plastic and then shattering it. Within a day, he had produced his first piece of safety glass, which he named "Triplex." This new type of glass consisted of two sheets of glass with a film of cellulose nitrate in between. Even if the glass broke, the pieces were held together by the plastic layer, preventing dangerous shards from flying apart.

In 1909, Benedictus obtained a patent for his invention, and Triplex went into production. However, automakers initially showed little interest in adopting safety glass for windshields due to the added cost. It wasn't until World War I that safety glass found its first practical, large-scale application in the lenses of gas masks. After seeing the performance of safety glass under extreme conditions, automobile executives finally recognised its value, and by the 1920s, Triplex became a standard feature in American automobiles.

Today, safety glass is commonly used in various applications, including windshields, side windows, goggles, and windows and doors in public buildings. It has played a crucial role in enhancing safety and reducing injuries in the event of accidents.

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