1. Main reason:
Double yellow lines are usually made of thermoplastic road markings, which contains tiny glass beads on the surface. The glass beads are so tiny that when it rains at night, the glass beads will be easily covered by rainwater and fail to reflect the light from vehicles. As a result, drivers of both sides are unable to identify the double yellow lines and cross the central lines unconsciously. Fail to reflect in rainy nights is the fatal shortcoming of thermoplastic road markings.
Fig. 1 Thermoplastic road markings are unrecognizable in rainy nights, and drivers may cross lane lines, or even central lines unconsciously.
2. Consequence of a collision:
If any vehicles cross the central line, it is quite possible that it could collide with another car from the opposite direction. If both of them are with speed of 60 km/hr, the accident severity equals to that of a car with speed of 120 km/hr hit against the wall.
3. The traffic authority knows
the shortcoming of the thermoplastic road markings very well and usually requests to install road reflectors of all kinds or recoverable plastic delineators on double yellow lines. Only that there is no national standard for recoverable plastic delineators, and they are said to be short-life.
Fig. 2 Road section where 360-degree tempered glass road studs are installed; S curve ahead is recognizable in a rainy night.
4. When the weather is good,
drivers could easily recognize all kinds of road markings, no matter it is day or night. If the weather is not good, especially when it is rainy and dark at night, accidents are more likely to take place. However, there are still people who are obliged to risk their lives to go out, including going out for work, for emergencies, for acute diseases, and other reasons. In rainy nights, not only central lines, lane lines, and sidelines become unrecognizable, but also the thermoplastic road markings are slippery for motorcycles due to the tiny glass beads on the surface.
5. In the early morning
of May 21st, 2020, a collision accident happened in Changhua County, Taiwan. A legislator from Changhua and her driver driving along the Taiwan County Highway 139 at 6 o'clock in the morning, their van collided with a car that "suspected to deviate from his lane and crossed the center line." One is dead and two are injured in this severe accident.
After investigation, there are many dangerous bends on the Taiwan County Highway 139, where car accidents occur frequently. Moreover, there aren't any road reflectors installed along the double yellow lines in the center at the said bends! If road reflectors are installed, cars would bump while driving over the road reflectors (bumping alert) for the road reflectors protruding from the road surface. As a result, the driver would realize that he has crossed the center line immediately, and serious collision accidents may be prevented!
Fig. 3 Road reflectors are not installed at the segment where the deadly collision occurred (Source: Chinatimes online news)
We hope this article could be presented to the officers of the traffic authority. If the importance of road reflectors is better understood, many car accidents are in fact preventable. After all, each car accident causes broken families and huge losses to the nation and society.
Per CNS13762, there are several types of tempered glass road studs applicable: 1) Type 25, protrusion height under 2.5 cm; 2) Type 19, protrusion height under 1.9 cm, which is ideal for lane lines or sidelines for its lower height.
Tempered glass road studs with protrusion height under 1.4 cm and under 0.9 cm are also available, whose compression strength and impact resistance could be tested according to CNS13762.