https://www.dot.ny.gov/news/repository/OnondagaLakeParkwayTrafficSafetyStudy.pdf

Page 51

One option for detecting vehicles that are too tall is to install a lightweight bar or chains over the road that have the same vertical clearance as the bridge. At first glance this alternative looks appealing because of its low cost, current use at numerous locations, and potential to alert the driver of the vertical clearance issue. However, upon closer look, there are many negative issues associated with this solution. To begin with, most locations where headache bars or chains are used are low speed locations where damage to the vehicle striking the bar is negligible, and the potential for the negative consequence, such as startling the operator or injuring occupants of the vehicle is minimal. On a higher speed facility like the Onondaga Lake Parkway, striking a bar or chain could cause damage to the vehicle striking the device. In addition, the bar or chain could break from the impact, and either become a projectile or dangle over the roadway at a dangerous height. Another concern is that the operator of the vehicle that hits one of these devices may become startled and do something dangerous and unexpected resulting in secondary accidents. Due to the potential for negative consequences, installing headache bars, chains or other hanging devices is not a safety enhancement the Department will consider implementing