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Window replacements

Understanding NJ TRANSIT Rail Car Window Issues

At NJ TRANSIT, we are dedicated to ensuring a comfortable, safe, and pleasant travel experience. One issue that has affected some of our trains is the appearance of cloudy or foggy windows, which can reduce visibility and impact your ride. We recognize how important this is to the quality of your commute. This page explains why this happens, particularly with single-pane polycarbonate windows, and details our plan to address the issue. 

Why Do Some Train Windows Become Cloudy? 

Several factors can cause windows on our trains to become cloudy over time. In many cases, this is due to the long-term effects of  UV light exposure and environmental conditions on single-pane polycarbonate glazed windows, which are the types of windows used on NJ TRANSIT trains and are standard in the transit industry. 

Here's why: 

  • Polycarbonate Material: Many train windows use polycarbonate, a strong, lightweight plastic known for its durability and impact resistance. However, unlike glass, polycarbonate is more susceptible to certain types of wear. 
  • UV Light Exposure: Constant exposure to ultraviolet (UV) light from the sun can cause the surface of polycarbonate windows to degrade. Over time, this can lead to a cloudy or hazy appearance due to the breakdown of the material. 
  • Scratching and Abrasion: Polycarbonate, while durable, can also accumulate scratches and abrasions from dust, debris, and frequent cleaning. These micro-scratches contribute to the window's opaque or dull look over time. 
  • Weather and Temperature Fluctuations: As our trains operate year-round, windows are exposed to extreme temperature changes. The expansion and contraction of materials during hot summers and cold winters can accelerate the aging process, further reducing clarity. 

What Did NJ TRANSIT Do to Come Up With a Solution? 

  • NJ TRANSIT collaborated with Rutgers University’s Center for Advanced Infrastructure and Transportation to investigate methods to restore window clarity. 
  • Testing focused on analyzing the polycarbonate-glass composite, evaluating cleaning methods, and identifying that the contamination of the glass coating was the primary cause of fogging and reduced visibility. 
  • The Conclusion: Restoration is not feasible as the windows have exceeded their useful life—replacement is the only viable option. 
  • NJ TRANSIT created an expedited replacement plan to minimize service disruptions, cutting the projected timeline from 6–8 years, down to 3 years, to complete the entire Multi-Level fleet. 
  • By studying installation techniques, optimizing workflow efficiencies, and addressing supply chain challenges, teams ensured a steady material supply and streamlined the installation process for consistent deployment. 

What is NJ TRANSIT's Plan to Replace Windows? 

Watch this 1-minute video to learn more about our plan 

  • NJ TRANSIT will replace more than 13,000 windows on the entire Multi-Level I and II fleet with 1/3 of the windows being replaced each year. 
  • The Multilevel II fleet will have their windows completely replaced by December 2025.

When Will You See Results? 

  • The windows on the Multilevel trains will be replaced on a rolling basis. Approximately a year from now, customers on our Multilevel trains will have a 1 in 3 chance of being in a car with new windows. In two years, Multilevel customers will have a 2 in 3 chance of sitting on a defogged window car. And in three years, every Multilevel customer will have unobstructed views. 
  • This is in addition to the 174 new Multi-Level III rail cars expected to begin arriving by the end of 2025.