Gateshead Speed Management Plan (SMP)
5. Engineering methods
In this section
Where speed surveys identify a speeding problem we will consider the introduction of engineering measures in order to slow traffic and ensure better adherence to speed limits. This will typically include one of or a combination of the following, although this list is not exhaustive;
Urban / village
Traffic calming measures
Vertical traffic calming
Vertical traffic calming can include road humps, speed tables, speed cushions or raised junctions. Each of these features protrude above the carriageway surface or form a new carriageway surface at a higher level than the former road surface and encourage vehicles to be driven over them at relatively low speeds.
Legislation only permits the installation of vertical traffic calming features on roads with a speed limit of 30mph or less and this approach is therefore only appropriate in urban, suburban and village locations.
When installing vertical calming consideration will be given to the road function and the level of use by buses and emergency vehicles. On bus routes only flat top humps with a table top of 10m or more or speed cushions will be permitted.
Although not a recognised traffic calming feature within the regulations we will also consider the use of raised street end treatments to reduce vehicle speeds turning into side streets whilst also providing at grade crossing facilities for pedestrians.
Horizontal calming and road narrowing
The introduction of horizontal deflections, particularly on existing roads that are long and straight, can be an effective way of reducing traffic speeds. These can include:
- build-outs
- chicanes
- islands/pedestrian refuges
- road narrowings/pinch points
- mini roundabouts
- road re-alignment
However, the use of build outs which give priority to traffic travelling in a particular direction, will only be implemented in combination with a vertical calming feature. Installation of priority features independently can encourage sudden acceleration and stop/start of vehicles. This is contrary to the aim of encouraging consistent lower speeds, can have adverse impacts on air quality and also increase levels of driver frustration.
Horizontal measures set out above are in the main limited to roads with a speed limit of up to 40mph, although certain measures such as islands, which encourage slower speeds without any sudden horizontal deflection will be considered on roads with higher speed limits.
Where deflections and narrowings are introduced consideration will be given to the types of vehicles using the route.
This will include:
- emergency services
- HGVs (including bin collection vehicles)
- buses
- abnormal load routes
- agricultural vehicles such as combine
- harvesters in rural locations
Street closures
Residential areas can often be used for through traffic or rat running and in situations such as this the traffic can have an adverse impact upon the community living on those streets, particularly where the speeds of vehicles is high. In such circumstances consideration will be given to the strategic closure of certain streets to reduce the impact of through traffic. A pilot scheme in London named 'Mini Holland' included numerous street closures in order to ensure through traffic was directed to main routes as opposed to residential streets.
Whilst such an approach can be used in isolation it is likely to be more effective as part of an area wide strategy and may also form one element of an area wide 20mph Zone scheme. Consideration must also be given to ensuring suitable access is maintained to properties and that issues such as deliveries and refuse collection can be accommodated.
On-street parking
Whilst not a speed management engineering measure per se on street parking can perform a speed management function by narrowing the road. We will, when considering the installation of waiting restrictions to prevent or restrict parking on the carriageway, consider the potential impact upon traffic speeds and whether on street parking should be allowed to continue (where it is safe to do so) or be restricted but with the need for other remedial measures.
On-street parking may however only occur during part of the day and will not calm traffic at other times. The restrictions set out in the Highway Code will still apply in these circumstances, that parking is not permitted: "opposite or within 10 metres (32 feet) of a junction, except in an authorised parking space".
Traffic-signals
We, as part of a 20mph Zone scheme on the A692 in Rowlands Gill, installed a signalised pedestrian crossing with speed detection capabilities. This enables the traffic signals to recognise the speed of oncoming vehicles and where a speed limit exceedance is detected will turn red in order to force the approaching vehicle to stop.
This occurs independently of the pedestrian crossing function and will occur even when there is no pedestrian waiting to cross. It is hoped that this will promote greater speed adherence. Subject to monitoring of this facility this approach will be considered at other locations.
Rural
Village gateways
Rural and semi-rural villages, particularly in the west of the borough are often segregated from one another by roads with speed limits in excess of 40mph. Managing the transition from high speed road to a limit of 20 or 30mph within a village or small settlement is key to ensuring drivers adhere to lower limit and drive safely throughout. We aim to introduce village gateway treatments on all village entries in rural and semi-rural locations.
A standard approach will be taken wherever possible to ensure continuity and achieve greater levels of driver recognition that a change in speed limit and environment is
occurring and in doing so influence drive behaviour.
The standard approach will typically involve a combination of:
- signage (speed limit, count down)
- fencing
- surface material changes
- bollards
- road markings (roundels, Dragons Teeth, transverse bar markings, hatching)
- rumble devices (more than 200m from residential properties)
Particularly in rural areas combined fencing and signage will be used in order to be more sympathetic to the surroundings.
In situations where the above measures are ineffective the addition of build outs and road narrowings will be considered.
Where the change in speed limit is significant a section of intermediate speed limit may be introduced in advance of the village gateway.
Bends
A major cause of accidents in rural areas outside of villages is motorists losing control on bends and leaving the road, and this can often be linked to vehicle speed.
Measures to make motorists more aware of the dangers of specific bends where speed is known to be a problem can be achieved through one or a combination of measures:
- bend warning signage
- chevron signs
- cats eyes
- bollards
- transverse or edge of carriageway road markings
At locations where the above measures are not successful in reducing speed related accidents consideration with be given to the introduction of an advisory speed limit or vehicle activated signage on the approach to the bend.
Whilst altering the road geometry can be considered this is unlikely to be feasible for reasons linked to land availability and cost. Other considerations could include the protection from or removal of roadside hazards such as trees in the vicinity of the bend. It is our approach to re-plant two new trees for every existing tree removed.
Quiet lanes
On lower class rural roads, particularly those that are narrow and lightly trafficked, consideration will be given to introducing quiet lanes, which can improve the environment for vulnerable road users such as horse riders and walkers.
Quiet Lanes will be considered in the following situations;
- Where there is strong community support
- 85th percentile speeds are below 35mph
- Traffic flows are below 1000 vehicles per day
- Road widths are below 5m
Quiet Lanes will typically include signage and discrete traffic calming such as road narrowing, central strips of vegetation, false cattle grids and fencing to encourage lower traffic speeds.
Urban / rural
Vehicle activated signs / driver feedback signs
Vehicle Activated Signs (VAS) provide illuminated feedback to drivers who trigger the sign when the vehicle approaches.
The aim of such signs is typically linked to two main purposes;
- Speed limit reinforcement- Actual speed, Slow down, smiley/sad face
- Hazard warning- bend, junction
VAS will only be considered when there is an accident problem associated with inappropriate speed that has not been satisfactorily remedied by standard signing and other engineering measures. VAS should not be used as a replacement for standard signage or as a speed limit repeater.
Due to high levels of ongoing maintenance and concerns over the long-term effectiveness of such signs the use of VAS will be limited to exceptional circumstances only and will not be widely used.
The use of VAS signs on a temporary basis with signs regularly rotated between different sites has been found to achieve the greatest speed reduction impact. The cost of implementing such an approach has not however been found to be cost effective and requires revenue funding not currently available.
Where VAS signs are installed this will be in accordance with the Department for Transport Traffic Advisory Leaflet 01/13 and TSRGD 2016.
Where VAS signs depicting actual vehicle speeds are installed, the signs will be set to give feedback up to 15mph above the speed limit to avoid instances of drivers attempting to attain higher speeds.
Road markings
Speed limit roundels marked on the carriageway surface can be a useful way of reminding drivers of the speed limit, particularly in areas where signage is ineffective due to vegetation or in order to minimise sign clutter in speed limits requiring repeater signs. Roundels are not permitted as repeaters within TSRGD regulations on roads where the speed limit is 30mph.
SLOW markings or transverse bar markings placed within the carriageway and dragons' teeth (Fig. 5.9) placed either side of the carriageway can be an effective means to encourage lower speed on an approach to a hazard or speed limit change.
Passive safety
We, in designing highway schemes on roads with a speed limit of 40mph or greater will, as part of a safe systems approach, include the use of products which meet Passive Safety standards. Such designs allow for driver error by reducing the severity of impact when drivers do lose control and leave the carriageway. The products are also designed to ensure that, when struck by a vehicle, they act in a controlled way and do not cause secondary injury.
Passively safe products typically include items of street furniture such as:-
- road signage supports
- street lighting
- bollards
- traffic signals
- cabinets
Certain Passively Safe products can also be designed to withstand impact and return to their original shape thus ensuring they continue to function for the purpose they were installed. This ensures that drivers continue to benefit from the warnings they provide, which could prevent further accidents occurring.