Traffic Management and Concrete Safety Barriers - Executive Summary
The objective of the study is to conduct a review with the aim of finding how the erection of temporary traffic management and permanent signing in the central reserve with concrete barriers should be managed. This review covers both wide and narrow central reserves and also considers aspects relating to power supplies and services.
This report presents a study that has investigated the issues of mounting signs on concrete safety barriers in the central reserve. The design of concrete safety barriers causes problems for the mounting of existing temporary traffic management signs since traditional sign mounting 'A' frames are considered to be unsuitable due to the height of the safety barrier. 'A' frames (which generally straddle the barrier) cannot touch the ground without modification. Various solutions to these problems have been investigated and are described in this report.
Concrete barriers have been widely used within mainland Europe for many years and have several advantages over steel safety barriers. They are narrower than two parallel rows of safety fence, and also do not deflect upon impact, freeing up valuable space for carriageway widening. Their inherent strength and impact resistance means they do not require repairs after accidents and as such are essentially maintenance free.
The solutions for temporary traffic management signs included the provision of temporary brackets to provide anchor points for conventional 'A' frames, retro-fit square post brackets for vertical type sign frames, eyelets mounted on top of the barrier, square post brackets pre-cast into the barrier during construction and establishing guidelines to make best use of current practice.
Permanent signs, such as matrix signals (MS1's), could be securely bolted down to the top of the concrete barrier using anchor bolts. Small permanent traffic signs could be installed into the top of the concrete barrier by fixing sign mounting posts into small diameter holes which are drilled into the top of the barrier and secured either mechanically or chemically using permanent adhesive.
Of the options discussed in this report, in cases where a wide barrier (approximately three times the width of a normal safety barrier) is used to accommodate lighting columns, vertically mounted sockets, built into the concrete safety barrier, to accommodate mounting posts for temporary traffic management signs is the favoured option, both in terms of ease and safe set up. However, in the cases of a normal width 'step' type safety barrier, a favoured solution is to use especially designed mounting brackets and straps to stabilise the sign mounting frames. An alternative solution is to mount steel eyelets on top of the barrier, to which securing straps could be attached to stabilise the sign frames.
Vertically mounting posts for permanent traffic signs, e.g. warning signs, can be appropriately positioned on top of the concrete safety barrier to allow for the laterally positioned re-enforcing bars in the barrier structure.
This report outlines the research and comprises four main areas:
- A study that has assessed current practice for mounting Temporary Traffic Management (TTM) signing on Vertical Concrete Barriers (VCB)'s. Current practices include the use of conventional sandbags plus webbing straps which tie sign frames to adjacent road furniture.
- A survey of TTM experts to gauge current opinions on the subject. Those consulted include National Highways Area Teams, the Traffic Management Contractors Association, Britpave, manufacturers of concrete barriers, and sign frame manufacturers.
- A questionnaire based survey of National Highways Area teams to establish the different types of permanent traffic sign located in the central reserve on the motorway and major trunk road network.
- A description and discussion of the various available solutions and recommendations for both permanent and temporary traffic management signs.