Highways Agency

Chapter 5 - Cost of Change in Provision

5.1 The Working Group considered the cost and practicality of the implementation of any change in the provision of safety barriers. For example, the introduction of a formal risk assessment methodology (as discussed in Chapter 3) might result in a different level of provision at a specific site than that provided by the existing standard. The Group decided to look at typical costs of additional provision of safety barriers.

5.2 The cost of work on existing major roads is highly dependent on the amount of traffic management that is necessary to safely carry out the work. For example, additional safety barrier provision on a motorway may involve closing the nearside lane while the work is carried out. Additional safety barrier provision on a minor local road may require traffic signals or even traffic diversions. This traffic management can be the largest element of the total cost and can vary greatly from site to site. A typical unit cost for the provision of an additional one metre of nearside safety barrier as part of the construction of a new motorway or trunk road bridge, say, could be about #pound;50, which is small in comparison to the cost of providing the new bridge. However, a typical unit cost for providing an additional one metre of nearside safety barrier on an existing motorway or trunk road, where specific traffic management will be needed, could be about #pound;250 (excluding any cost of delay to traffic as a result of the work).

5.3 The difference between these two unit costs is largely the result of the difference in approaches that would be required. Each additional length of safety barrier provided at a new bridge would be installed to best fit with the construction of the bridge and would be done as part of the overall work being carried out. Installation of additional lengths of safety barrier on the existing motorways and trunk roads would probably have to be carried out as discrete elements of work. This would not only require separate traffic management (lane closures, traffic signals, traffic diversions) but would also have to include the removal of existing barrier anchorages and dealing with any public utility apparatus. There is an additional risk arising from the work required to install additional barriers, to both the road user and the workforce carrying out the installation. These risks would need to be included in any risk assessment.

5.4 Having identified the need for the adoption of a more robust risk assessment, which will identify both the costs and benefits of barrier provision at particular locations, the Group was not in a position to quantify the extent of barrier that might be required or its overall cost. However, from the unit costs, it was clear that costs from any changes to the level of provision of safety barrier arising from their recommendations are likely to be reasonably low.

5.5 Generally, revised standards only apply to roads that are built after the date of introduction of that standard; they are not generally applied retrospectively. In this particular case the Group considered that their recommendations should apply to work carried out on the existing road network as well as to new works.