In 1960, the department began an investigation to develop the optimum type of barrier for narrow medians and to improve all railings in order to reduce impact severity. By 1966, five new types of railings had been developed, tested, and placed in service. The full scale tests, performed at maximum anticipated speed and angle, had demonstrated the superior performance of the newly developed barriers. However, since most impacts occur at less than maximum conditions, it was considered necessary to compare field performance and repair costs of the new style barriers with the older type railings. Before launching a long term investigation, a pilot study was undertaken to evaluate the data collection method proposed for such a survey. Although only a limited quantity of accident data were collected for new barriers, the data collection method appeared to be entirely adequate. In addition, the limited data indicates that: (1) there is a definite reduction in accident severity for collisions with the new highway barriers, (2) there seems to be very little difference in barrier damage when comparing collisions with new and old style cable guide rail. Therefore, repair costs are expected to be approximately the same, and (3) box beam barriers required little maintenance, in spite of the fact that on the expressways and parkways, they have been hit frequently. /Author/.
Samenvatting