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Engineering

London Road Safety Unit

TLRN engineering

The flow chart below gives a brief explanation of each stage of the engineering process.

Process

Engineers use collision data (from the data and research team) to identify sites in London with the highest number of collisions and casualties in the last 36 months. Sites are put into a priority order and engineers begin working on those that are identified as highest risk to road users.

A collision map is created for each site (click on the link below to see an example of this collision 'plot').

Collision Plot (PDF - 1.5MB) A detailed analysis of each collision is carried out. Engineers look at many things, including the direction vehicles were travelling in, the time of day and who was involved in each collision.
Engineers make site visits to observe the traffic and local highway conditions. These visits allow engineers to relate collision data to the actual location. It also allows engineers to see how vehicles and other road users behave at the site.
Recommendations for road safety engineering measures (for example traffic calming, road markings or amended signage) are made. Engineers estimate how much the collisions would reduce by at each site, if the measures were installed. A projected financial saving is also made.
Road safety engineers produce a report for each site they have analysed. This contains the collision plot and analysis of collisions, details of site visits and recommendations for road safety engineering measures. This report is passed to TLRN Planning Unit and Road Network Management. They arrange for detailed design work to be carried out and for the scheme to be constructed.

After construction, engineers from LRSU visit the sites to make sure everything is to standard and to take photographs. The number of collisions at the site is monitored for the next 36 months. Engineers then use this data to check that the engineering measures are working as they should and that collisions have reduced.

If any road safety issues remain during the monitoring period, further investigation will take place.

Engineers work in three Teams, covering North, Central and South London boroughs.

North

Waltham Forest, Redbridge, Havering, Barking and Dagenham, Newham, Hammersmith and Fulham, Hounslow, Hillingdon, Ealing, Brent, Harrow, Barnet, Haringey, Enfield.

Central

City of London, Westminster, Camden, Islington, Hackney, Tower Hamlets, Southwark, Lambeth, Wandsworth, Kensington and Chelsea.

South

Greenwich, Lewisham, Bexley, Bromley, Croydon, Sutton, Merton, Kingston upon-Thames and Richmond-upon-Thames.

Projected financial saving
The estimated cost of an urban injury collision (including an allowance for damage-only collisions) is £93,531 at 2008 prices. When LRSU engineers recommend engineering measures, they look at how many collisions might be prevented if the scheme is installed. This allows them to calculate the estimated financial saving of a scheme. The physical, social and emotional consequences cannot be quantified.
TLRN planning unit
The planning unit is responsible for coordinating all improvement schemes on the TLRN. When a road safety engineering scheme is passed to them, they look to see if any other schemes are being installed in that area, or if TfL are doing any other work at that location. They can also prioritise schemes.
Road Network Management (RNM)
Once an LRSU collision study has been completed it is passed to RNM. Recommendations made by road safety engineers are looked at by RNM and taken forward through production of detailed designs (this has to be completed before a scheme can be installed).