GB2304769A - Traffic calming device - Google Patents

Abstract

A traffic calming device (2) comprises ramp members (38) movable between a first, raised position, maintained by a resilient means (20,22,24) situated in a cavity (18) in the road beneath the ramp members (38) and a second position in which the ramp members (38) lie substantially level with the road surface. A sensor means (15) senses the speed of an approaching vehicle. If the speed is below a given limit the weight of the vehicle causes the ramp members (38) to retract from the first position to the second position. For a vehicle travelling above the given speed limit a locking means (30) maintains the device in the raised first position until the vehicle has passed over.

Description

IMPROVEMENTS RELATING TO TRAFFIC CALMING This invention relates to a device for reducing the speed of vehicles, and to a method of operating the device.

Various means for calming traffic, that is reducing its speed, in speed sensitive areas are well known. For instance the provision of raised portions of road, often known as "humps" or "sleeping policemen" is a common solution. Such a device does however, suffer from limitations. The hump presents a hazard which can only be negotiated safely, by a vehicle, at low speeds. A hump of this nature, usually fabricated from concrete, tarmac or similar, is a permanent feature of the road.

Therefore the humps provide an obstacle for all vehicles passing across it, including emergency service vehicles, vehicles carrying fragile cargo or disabled persons and vehicles driving within the speed restrictions of the area. Obviously reducing the speed of emergency service vehicles is not desirable and known humps also penalise drivers who choose to obey speed restrictions applied in that area.

It is an aim of the present invention to provide an improved traffic calming device for use in speed sensitive areas.

According to a first aspect of the invention I provide a traffic calming device which has a surface moveable between a first position proud of the road surface and a second retracted position, the first position providing an obstacle for vehicles passing across the device.

An advantage of such a device is that it may be moved to the first position to provide an obstacle to traffic as desired, and therefore be operative against traffic exceeding a given speed limit.

Preferably a sensing means is provided to determine the speed of vehicles approaching the device.

The device may be moved between the first position and second position according to the sensed speed of a vehicle. Such a device has the advantage that only vehicles travelling in excess of a given speed will be subject to the obstruction.

Preferably the device is normally in the first position and is retained in that position when the sensed speed of an approaching vehicle exceeds a given limit, the device being moveable to the second position when the sensed speed is at or below the given limit.

In the second position the device may be substantially level with the surrounding surface thereby offering minimum obstruction to vehicles passing across the device within the given speed limit.

Preferably the device uses the weight of the vehicle to move the device from the first position to the second position.

A means may be provided which causes the device to assume the second position irrespective of the speed of an approaching vehicle as the vehicle passes over the device. This may allow emergency vehicles to pass across the device, unobstructed, despite travelling in excess of the threshold speed which would normally cause the device to be maintained in the first position.

Preferably vehicles approaching from different directions, for instance on opposite sides of the road, may be obstructed independently. This will allow vehicles to be obstructed simply according to their speed. Vehicles travelling at a speed below the activation threshold in one direction would not be obstructed simply because a vehicle travelling at a speed above the activation threshold were passing the device at the same time, but in the opposite direction.

Preferably the device assumes the first position under the influence of a resilient means such as a spring, or fluid pressure means.

In one embodiment of the device a means is provided to lock the device in the first position, preventing it moving to the second position when the sensed speed of an approaching vehicle exceeds the given speed limit.

According to a second aspect the invention consists in a method of traffic calming by selectively obstructing vehicles according to their speeds.

An example of a traffic calming device according to the invention is illustrated in the accompanying drawings in which:- Figure 1 is a perspective view of a traffic calming device installed across a road; Figure 2 is a side view of the mechanism operating the device of Figure 1, in a normal first position; Figure 3 is a side view of the mechanism operating the device, locked in the first position; and Figure 4 is a side view of the mechanism of Figure 1 in the second position.

A traffic calming device is now described, with reference to Figures 1 to 4, which is retractable from a first position, to provide an obstruction to vehicles, to a second position allowing vehicles to pass unobstructed.

Figure 1 shows the traffic calming device 2 installed across the entire width of a road 4. The device 2 has two portions 6,8 to control the vehicles travelling in opposite directions along either side of the road. The portion 6 is shown raised in the first position so that vehicles passing across the device 2 are obstructed. The portion 8 is shown in the retracted second position, allowing vehicles to pass across the device unobstructed. The lines 10,12,14,16 across the road represent the position of sensing means which are used to determine the speed of vehicles travelling toward the device, and sensing when both axles of the vehicle have passed over the device.

A receiving means 15 is provided to receive signals from vehicles approaching the device.

Controlling means 17 are provided to monitor signals from the sensing means 10,12,14,16 and the receiving means 15.

Figure 2 shows the device 2 locked into the first, obstructing, position. A cavity 18 is provided in the ground where the device is to be installed. The cavity 18 provides a housing for a sliding member 20, a helical spring 22 and a guide 24. The lower portion 26 of the guide 24 is of a larger cross section than the upper portion 28.

The spring 22 urges the sliding member 20 in an upwards direction.

Locking means 30 are provided in an upper portion of the cavity. In the embodiment shown the locking means 30 comprise solenoids, consisting of a coil 32 and plunger 34. The sliding member 20 has recesses 36 which are dimensioned so that they can co-operate with the plungers 34 of the locking means 30.

Secured above the ground are members 38 which can form a ramp for the traffic calming device. In the first position, as shown in Figures 2 and 3, the sliding member 20 occupies an upper portion of the cavity 18 and protrudes above the level of the ground to support the members 38 in their ramp configuration. The top portion of the sliding member 20 is configured to co-operate with the members 38.

The various electrical devices (locking, sensing and receiving means) are supplied with electrical power from a nearby power supply. It will be appreciated that most traffic calming measures are constructed in built up areas where there is an adequate electricity supply.

In operation the traffic calming device 2 is normally set in the first position, as seen at 6 and in Figure 2. The plungers 34 of the solenoids are retracted from the cavity 18. The sliding member 20 is therefore free to move from the first position and move towards the second position as shown in Figure 4 if a force is applied on a substantially downward direction.

As a vehicle approaches the traffic calming device 2, the vehicle must pass across the sensing means 10,12,14,16. The sensing means pass across the entire width of the road so that a driver cannot drive along the wrong side of the road to approach the device 2 undetected, which would be possible if the sensing means covers only half of the road.

The sensing means signals the controlling means 17 which determines (for instance by timing the time taken to cross between the sensors) the speed of the vehicle approaching the device 2. If the vehicle is above a threshold speed then the plungers 34 are extended to such a position where they co-operate with the recesses 36 in the sliding member 20. The sliding member 20 is therefore locked in the first position and cannot slide downwards to the second position. As the vehicle passes across the device 2, because the sliding means 20 is prevented from travelling downwards, a ramp is presented to the vehicle. The ramp provides a similar effect to the usual "sleeping policeman" and the driver of the vehicle is alerted to their excessive speed.

However, if the vehicles speed is below the threshold value the controller means maintains the plungers 34 in a position outwardly of the cavity 18 and out of contact with member 20. The spring 22 maintains the sliding member in the upper portion of the cavity 18. As the vehicle crosses the device, the downwards force exerted by the vehicle, on the sliding means, is greater than the upwards force exerted by the spring 22. The sliding member is therefore caused to move to the lower portion of the cavity 18, to the second position. Thus, a flat surface is presented to the vehicle which may pass across the device with a minimum of obstruction.

The device shown at 8 in Figure 1 has adopted the second position, as if the wheels of a vehicle were crossing the device, however, the vehicle has been omitted for clarity.

The guide means 24 passes into the sliding member 20, as the sliding member 20 moves downwards, preventing rotation of the sliding member 20 which would cause the device 2 to jam. The lower portion 26 of the guide means acts as a stop, preventing the sliding member from travelling too far in a downwards direction. The lower portion 16 also defines a space which is occupied by the compressed spring.

Once the wheels of the vehicle have passed across the device 2, no downwards force will be exerted on the sliding member 20. The spring 22 will urge the sliding member 20 into the first position causing the ramp to appear. After an elapsed time, or perhaps after the vehicles pass across the next sensors, the device will be ready to operate.

Spring 22, member 20 and guide 24 act as a damper mechanism, (such as on a car suspension system) that enables the member to return to the raised position smoothly.

In a different embodiment the plungers 34 of the solenoids may be extend into the sliding member 20 in the device's normal state. The plungers 34 would then be retracted from the sliding member if an approaching vehicle had a speed below the threshold level. If however the approaching vehicle has a speed above the threshold value the plungers would remain extended, causing a ramp to be presented to the vehicle.

Emergency vehicles, for example, may be supplied with devices to signal the receiving means.

If the receiving means 15 receives such signals the control means 17 will be alerted to the approach of the vehicle. The sliding member 20 can therefore be maintained in a released state allowing the ramp to collapse to the second position and unobstructed passage of the vehicle is permitted, despite the approaching vehicle travelling at a speed above the threshold value. It will be appreciated that such devices fitted to emergency vehicles may only check the receiving means for the signal from an emergency vehicle, if the sensing means detects a vehicle approaching which is travelling above the threshold speed.

It will be appreciated that various different sensing means may be used to determine the speed of approaching traffic. Examples of sensing means which may be suitable include: radar, infra red, pressure sensing or electrical contacts. Such sensors are well known in the art of detecting traffic, for instance for traffic control signals or speed cameras.

Means other than solenoids, of locking the device into the first position may be used.

Envisaged possible alternatives would be pneumatic, hydraulic or other mechanical means.

If the device is situated in a remote area, a power source may need to be supplied for the device.

Any means of supplying adequate power to the locking means, receiving means and sensing means will be suitable. For instance batteries, solar cells or generators may be provided. In a different embodiment the means which require electricity may be removed and the device operated through mechanical means. That is the weight of the vehicle passing over a sensor may be used to lock the device, or inertia may be used (as for example in car seat belts).

Claims (13)

1. A traffic calming device comprising a surface which is movable between a first position proud of the road surface and a second retracted position wherein the first position provides an obstacle for vehicles passing across the device, a sensing means to determine the speed of vehicles approaching the device, wherein the device is moved between the first position and the second position according to the sensed speed of the vehicle.

2. A traffic calming device according claim 1 wherein the device is normally in the first position and is retained in that position when the sensed speed of an approaching vehicle exceeds a given limit.

3. A traffic calming device according to claim 1 or claim 2 wherein the device is at or is movable to the second position when the sensed speed is at or below a given limit.

4. A traffic calming device according to any preceding claim wherein the second position of the device is substantially level with the surrounding surface.

5. A traffic calming device according to claim 3 wherein the device is moved from the first position to the second position by the weight of a vehicle.

6. A traffic calming device according to any preceding claim comprising means permitting the device to assume the second position irrespective of the sensed speed of the vehicle.

7. A traffic calming device according to any preceding claim comprising two portions one on each side of the road wherein vehicles approaching from opposite directions are obstructed separately.

8. A traffic calming device of any preceding claim wherein the first position is assumed under the influence of a resilient means.

9. A traffic calming device of claim 8 wherein the resilient means is a spring.

10. A traffic calming device of claim 8 wherein the resilient means is a fluid pressure means.

11. A traffic calming device of any preceding claim comprising means to lock the device in the first position.

12. A traffic calming device substantially as defined herein and with reference to the figures.

13. A method of traffic calming comprising selectively obstructing vehicles according to their speeds.