Road Restraints Risk Assessment Process (RRRAP)
The Risk based Road Restraint Systems Standard does not follow the traditional standard format. The Standard has two parts that must be used together,
- The written Standard TD19 'Requirement for Road Restraint Systems', which contains some mandatory requirements but gives mainly advice and guidance and the
- 'Road Restraint Risk Assessment Process (RRRAP)', which is in Excel, and enables the Designer for each site/scheme to establish the need for a vehicle restraint and, if so, its performance requirements.
The RRRAP tool is now released and the TD19/06 document is live and replaces IRRRS.
The Road Restraint Risk Assessment Process is available to download as a Microsoft Excel file, therefore you will need a copy of Microsoft Excel to use it. At over 5 MB the file is quite large so it may take a while to download on slower internet connections.We are also providing a compressed version of the file in Zip format which will download faster, but you will need a copy of WinZip or similar software to unpack the file.
If you have any trouble downloading the file, it is most likely due to your security settings not allowing you to download ZIP files or Excel files with macros. In this instance please contact the Road Restraints Team (contact details below) and request a copy of the files on CD.
Note that various Aggressiveness factors for hazards were modified between RRRAP Issue 1.3 and Issue 1.3a to remove anomalous and unexpected results.
To assist users of the RRRAP to copy input data from an old version of the RRRAP to the latest version, the following Excel worksheet may be used. This contains macros that will copy parts or all of the data from the old version of the RRRAP (the old file must be temporarily named OSP.xls into the new version of the RRRAP (the new file must temporarily be called NSP.xls). The temporary names can be changed to suit once the data copying is complete.
The help Guidance Manual is available below and this will take you through a step by step process of using the RRRAP.
If you have any questions or problems with the RRRAP then please consult the RRRAP problem check sheet for commonly encountered problems before contacting us.
This worked example is a spreadsheet with basic details already filled out such that it is validated as functional in being able to calculate those entries already populated. It can be used to verify IT system issues or examine problems with data entry.
Advice on the use of TD 19/06 in Northern Ireland
In Northern Ireland TD 19/06 and the RRRAP was implemented from 1st August 2007. For further information please contact the Engineering Policy Branch, Tel. 028 90540405.
Advice for Low Flow Trunk Roads in Wales and Scotland
The RRRAP allocates an aggressiveness value to each hazard adjacent to the road and quantifies risk by estimating the equivalent fatalities per vehicle km. For very aggressive objects adjacent to high speed roads, the RRRAP indicates that the provision of a Vehicle Restraint System (VRS) is required to lower the risk to an acceptable level, regardless of the traffic flow.
However, as traffic flow decreases the benefit/cost ratio of solutions also decreases. This is because although the overall risk decreases when a VRS is provided, the benefit is relatively small due to the relatively low number of accidents it prevents. Therefore, where two-way traffic flows are less than 5,000 AADT the designer should; assess whether the output from the RRRAP are practicable, if the benefit/cost ratio results warrant VRS provision and discuss their findings with the Overseeing Organisation.
This does not apply to the provision of parapets.