Expanding the Use of Wire Rope Barrier Systems
Photo 1. Wire rope barrier system
Photo 2. Installation of sleeves, posts,
Photo 3. Pipes for existing bridges
Head-on collision accidents often lead to fatalities. In order to prevent such accidents, we developed wire rope barrier systems as a prevention measure that can be implemented in a small space at a small cost (Photo 1).
Wire rope barrier systems consist of steel pipes (sleeves) inserted into the ground and wire ropes, which run through slits in the upper part of the posts and are fixed and tensed at the end (Photo 2). Wire rope barrier systems have the following characteristics.•When a vehicle collides into the barrier, the posts bend and mitigate the shock. The shock incurred by the passenger is reduced compared to conventional traffic barriers. •It can be installed in a smaller space as the posts are thinner and there is no front or back parts to it. •In accidents and other emergencies, the wire ropes can be removed by hand, making it possible to create an opening in the barrier anywhere needed. •If damaged in an accident, etc., the barrier can be restored just by replacing the bent posts and re-tensing the wire ropes. This process can be completed by hand in a short time.
Wire rope barrier systems drew attention following the recommendation of the Board of Audit (BOA) to the Ministry of Land, Infrastructure, Transport and Tourism (MLIT) and other agencies in FY2014. The BOA pointed out that there had been frequent traffic accidents involving vehicles drifting out of one lane into the opposing lane in temporary two-lane expressways. The BOA recommended the improvement of the safety and functionality of these roads. In response to this recommendation, the MLIT announced in December 2016 a pilot project to introduce wire rope barrier systems as lane dividers to replace conventional rubber posts. In FY2017, wire rope barrier systems were introduced along approximately 113 km of the temporary two-lane zones (earthwork sections) managed by NEXCO(Nippon Expressway Company Limited). The MLIT Advisory Committee on Preventive Measures for Head-on Collisions on Highways reported that the number of accidents involving vehicles drifting to the opposing lane decreased from 45 to 1 from the previous year, and that the number of fatal accidents and of injuries decreased from 7 and 6 to 0, confirming the effect of wire rope barrier systems to prevent head-on collisions.
In order to install pilot barriers in the existing bridges to examine their effects, we needed to develop a method to install the barriers without affecting the floorboard. Therefore, we developed a foundation that is thinner than the pavement and posts with base plates that are weaker than the posts (Photo 3). After the effect of this technology was verified by the Advisory Committee, this technology was also tested with existing small- and medium-sized bridges.
In June 2018, the MLIT announced that wire rope barrier systems would be installed in all of the earthwork sections of the temporary two-lane expressways that were to be opened from then on, except for the zones where reformation into four lanes or construction of additional lanes were ongoing. It also announced that wire rope barrier systems would be installed in already operating sections for approximately five years (approximately three years for expressways managed by NEXCO).
In the future, we will work on technological development in order to solve the issues that were identified in the pilot project.
(Contact:Traffic Engineering Research Team, CERI)