GB2350425A - Apparatus for warning of the risk of collision of a moving vehicle with a staionary vehicle - Google Patents

Abstract

Collision warning system, especially suited for roadside use, which gives a warning when it is determined that a moving vehicle may collide with a stationary vehicle. The stationery vehicle may be a broken down vehicle, for example on a motorway hard-shoulder. The determination of a possible collision is made by detecting sound emitted from the moving vehicle, for example using a directional microphone.

Description

2350425 COLLISION ALERT This invention relates to the early warning of a

collision or potential collision.

An increasing number of injuries and deaths are occurring when an operator of an emergency service works on a vehicle on the hard shoulder of major roads and motorways. Thus, when a vehicle is stopped on the hard shoulder, vehicles in the inner lane may pass so closely that they may hit the operator. It is even more serious if a vehicle strays onto the hard shoulder and therefore collides with the stationery vehicle or the patrol vehicle.

In the case of our patrol force, a large number of patrol calls are for punctures where the member has no means of replacement or temporary repair, or either is incapable or unwilling to attempt repair themselves. Here it is essential, therefore, for a patrol to work on the vehicle before it can be moved to a safer location.

What is required, therefore, is a means of warning the patrol that a vehicle is travelling in a direction and at a speed which is a threat to the area where a patrol is working while attending an incident on major road, e.g. the space required in order to manoeuvre around stationary vehicles to replace a road wheel. The warning will also need to alert the patrol quickly enough to enable the patrolman to position himself in a safe position away from the breakdown in order to assess the situation further.

A number of possible solutions have been suggested, ranging from laser measurement to microwave. Both can be utilised to some degree, although both will be greatly affected by adverse weather conditions, as well as creating difficulties with licensing and health and safety.

The use of laser for speed and distance measurement could provide a very fast and accurate method of threat detection, although the cost to produce and the need for accurate aiming cause concern. It is also unclear as to the legal or health implications of possible damage to sight or involuntary vision impairing that could be caused by even low wave length laser emissions, although a system of speed measurement is being used by the police. Laser early warning devices require careful sighting and relatively good conditions in order to be effective, even mild fog and mist can cause sufficient defraction of the emitted beam to cause inaccurate or even ineffective measurement.

Microwave radio utilising the Doppler effect is also a very highly recommended method of threat determination. The use of directed radio above 10 GHz can be used to determine speed and distance from a moving target. However, the cost of creating both a directional emitter and receiver becomes larger with both directionality and sensitivity.

According to the invention the sound emitted by a moving vehicle is detected by apparatus which then determines from the sound whether that moving vehicle is liable to collide with a stationary vehicle, and in the event of the possibility of collision being determined the apparatus gives an immediate warning.

Also according to the invention, a method of detecting a risk of collision by a moving vehicle with a stationary vehicle is provided in which the noise emitted by the moving vehicle is detected and from this the path of the moving vehicle is determined, this is compared with the position of the stationary vehicle to determine if a risk of collision exists, and in the event that it does, a warning is given.

Apparatus for determining a potential risk of collision with a stationary vehicle in one embodiment comprises directional microphone means, means for filtering and conditioning the output signal from the microphone means to determine parameters such as speed, direction and distance of an oncoming vehicle, comparing those parameters with predetermined parameters to decide if the oncoming vehicle is liable to collide with the stationary vehicle, and means for providing an immediate warning in the event that a possible collision is detected.

All road traffic creates noise consisting of a wide range of audible frequencies. This noise can be used to identify the sources, direction and speed of a given vehicle, while utilising rather simpler electronics than is required by either laser or microwave technology, but still maintaining a high degree of accuracy. This can be achieved by using one or more highly directional audio pickups mounted at predetermined locations on the patrol vehicle. The received signal requires a high degree of filtering and conditioning before presentation to a microprocessor that will be used to determine the speed, direction and distance of any object moving within a pre defined directed field of observation, and then derive whether the object is indeed a threat. From the information that is gathered and analysed it is possible to listen to the traffic and determine in advance when a travelling object is moving towards the defined area of a stationary patrol.

The audio pickups will need to be designed to listen in a very tight reference area to a narrow, audible frequency bandwidth. The pickups are designed to provide as high a gain as possible in the region of best overall frequency to listen for in the overall audio spectrum analysis of road noise.

A suitable pickup is a line microphone as shown in Figure 1 of the accompanying drawings. It utilises an approximate line of equally spaced pickup points connected through acoustically damped tubes to a common microphone diaphragm. The phase relationship at these points for an incident planewave combine to give a sharply directional pattern along the axis if the line segment is at least one wavelength of the listened to frequency. The optimum listening pattern is pictured in Figure 2 of the accompanying drawings and is shown providing a listening angle of 5 degrees.

The microphone acoustic properties will be such that it provides a narrow listening frequency (fx). The returned audio signal will then be filtered through an active bandpass filter that has very fast cutoff frequencies to provide a signal as shown in Figure 3 of the accompanying drawings, with stop band edge decays of a high magnitude. In order to meet this requirement a filter network that utilises the Chebyshev filter design, with a high order polynomial greater than 10 and low passband ripple of 0.5 db, is preferred.

The directional microphones are desirably mounted on the rear of a patrol vehicle so that the "path of sensitivity" has an unobstructed view back along the hard shoulder and the road. In that connection, it is standard practice for a patrol vehicle to be parked a short distance behind the broken down vehicle to act as a barrier. However, a high speed vehicle colliding with such a patrol vehicle may still have sufficient momentum to push that patrol vehicle and the colliding vehicle into the vehicle under repair.

Preferably two or more pickup microphones are provided to listen to the road noise.

Objects passing across the paths of sensitivity will create noise pulses.

During this time, the pulses received would be ignored as this signifies normal traffic noise. Any object that travels along the path of sensitivity will create a steady noise of increasing magnitude. The magnitude of sound will dictate the object distance, while the increasing audio ratio can be used to calculate the speed of approach.

For example, two microphones P1 and P2 can be mounted onto a patrol vehicle 3 as pictured in Figure 4 of the accompanying drawings.

Microphone P1 is responsible for sighting directly down the carriageway side viewing the hard shoulder. Its pickup beam 4 is shown. The other microphone P2 is mounted viewing across the carriageway at an angle approximately 20 degrees negative to a central line and its pickup beam 5 is shown.

Microphone P2 will therefore be looking for objects moving diagonally across a carriageway at an angle of impingement towards the patrol danger zone.

In order to identify a threat as early as possible, the range of detection will need to be quite extensive. With the directionality and active filtering a high gain amplifier will be used in order to provide a usable detection distance.

The detection distance will be dependent upon both atmospheric pressure and air density, and as such automated measurement adjustments can be added to the detection system for automatic gain adjustment due to changing weather conditions.

A patrol will require a reasonable amount of time in order to realise that a warning of a possible threat is being given and to move to a safe position. Understanding that at 70 mph an object will be moving at 34 meters a second, and that an impact time of less than two seconds would be very unlikely to provide enough reaction time for both the patrol or threat to take evasive action, the minimum monitoring distance would need to be of an order greater than 3 seconds, equating to 103 meters in distance. More preferably a minimum sensing distance of 150 meters providing a minimum listening distance of 4.4 seconds in all conditions is required.

Once a threat of collision is detected a loud sound warning to the patrol is required.

Claims (11)

CLAIMS:

1. Apparatus for determining a potential risk of collision by a moving vehicle with a stationary vehicle in which the sound emitted by the moving vehicle is detected which then determines from the sound whether that moving vehicle is liable to collide with the stationary vehicle, and in the event of the possibility of collision being determined the apparatus gives an immediate warning.

2. Apparatus for determining a potential risk of collision with a stationary vehicle comprising directional microphone means, means for filtering and conditioning the output signal from the microphone means to determine parameters such as speed, direction and distance of an oncoming vehicle, comparing those parameters with predetermined parameters to decide if the oncoming vehicle is liable to collide with the stationary vehicle, and means for providing an immediate warning in the event that a possible collision is detected.

3. Apparatus as claimed in either preceding claim which includes one or more highly directional audio pickups mounted at predetermined locations on a patrol vehicle.

4. Apparatus as claimed in Claim 3 in which the received signal is filtered and conditioned before presentation to a microprocessor used to determine the speed, direction and distance of any object moving within a pre-defined directed field of observation, and then derive whether the object is indeed a threat.

5. Apparatus as claimed in Claim 3 or Claim 4 in which the pickup is a line microphone utilising an approximate line of equally spaced pickup points connected through acoustically damped tubes to a common microphone diaphragm.

6. Apparatus as claimed in any of claims 2 to 5 in which the audio signal is filtered through an active bandpass filter that has very fast cutoff frequencies with stop band edge decays of a high magnitude.

7. Apparatus as claimed in any preceding claim in which directional microphones are mounted on the rear of a patrol vehicle so that the path of sensitivity has an unobstructed view back along the hard shoulder and the road. 10

8. Apparatus as claimed in Claim 7 in which a vehicle travelling along the path of sensitivity will create a steady noise of increasing magnitude, the magnitude of sound dictating the object distance and the increasing audio ratio being used to calculate the speed of approach 15

9. Apparatus as claimed in any preceding claim in which the minimum monitoring distance is greater than 3 seconds.

10. Apparatus as claimed in Claim 9 in which a minimum listening distance of 4.4 seconds in all conditions is provided. 20

11. A method of detecting a risk of collision by a moving vehicle with a stationary vehicle in which the noise emitted by the moving vehicle is detected and from this the path of the moving vehicle is determined, this is compared with the position of the stationary vehicle to determine if a risk of collision 25 exists, and in the event that it does, a warning is given.