GB2273190A

GB2273190A - Traffic information system

Info

Publication number: GB2273190A
Application number: GB9225577A
Authority: GB
Inventors: Neil Andrew Moss; Adrian Russell Moss
Original assignee: Individual
Current assignee: Individual
Priority date: 1992-12-07
Filing date: 1992-12-07
Publication date: 1994-06-08
Also published as: GB9225577D0

Abstract

A road traffic information system uses a network of short-range radio transmitters at or near permanent road signs, such as those indicating speed restrictions, or temporary traffic hazards. Each transmitter transmits continuously an encoded signal corresponding to one of a set of possible mandatory or advisory output signals. Each vehicle using the system carries a receiver tuned to the transmitter frequency, and incorporating a decoder. The decoder output signal selects one of the same set of preprogrammed output signals, and causes the driver to be sent an appropriate auditory and/or visual signal to complement those he receives from his environment.

Description

TRAFFIC INFORMATION SYSTEM This invention relates to a traffic information system comprising a network of roadside transmitters intended to signal road hazards etc. to the drivers of vehicles equipped with receivers tuned to the wavelength at which the transmitters operate.

Each transmitter is intended to be sited either permanently near a speed-restriction sign or like advisory or mandatory warning, or temporarily near a road-traffic accident or flooded road etc. forming a traffic hazard. The transmitter operates at a wavelength at which its transmitted signal becomes too attenuated to be useful over distances in excess of about 50 m, such as at 418 MHz, of which the range is of this order, and certainly less than line-of-sight. The transmitter generates a coded pulsiform signal having an envelope which is specific to one of a range of predetermined warning or advisory signals, and transmits this signal continuously at a chosen repetition frequency.

Each receiver for use with this system is intended to be mounted in a vehicle. The receiver aerial can be mounted discreetly on the vehicle, such as on its front bumper, because the vehicle is always approaching each transmitter. Because of the high frequency at which the system operates, the aerial need only be short, of about 150 mm maximum length. After the received signal reaches an input threshold value, it is decoded and produces an output signal (which may be visual and/or auditory) which is specific to the transmitter which has come within range. Each receiver has available to it a range of alternative pre-programmed output signals, and selection is made of that signal which is specific to the hazard etc. being approached.

The present invention aims at providing a traffic information system in which the driver of a vehicle fitted with the correct receiver is advised of traffic hazards or restrictions in a way in which complements the usual visual signals which the driver detects. In-this way, any visual signal which the driver might miss, because of being temporarily distracted or having a road sign blocked from view by intervening vehicles, is conveyed to the driver by a route not likely to be affected by these other factors. Such redundancy leads to increased traffic safety.

Accordingly, the present invention provides a traffic information system comprising a plurality of short-range radio transmitters positioned alongside a road system, each transmitter being adapted to transmit a coded signal indicative of a speed or other restriction or warning pertaining to the length of road in the range of or adjacent the transmitter, and a plurality of signal receivers each intended to be carried by a vehicle and to generate from the received signal an output signal advising the driver of the vehicle of the restriction applying to the section of road over which he is travelling at the time his receiver detects the transmitted signal.

The present invention will now be described by way of example with reference to the accompanying drawing, which is a diagrammatic view of a transmitter and receiver of the present invention in operational range of each other.

In the drawing, a transmitter 2 is intended to be positioned alongside a traffic sign, either a temporary or a permanent one. The transmitter may receive either mains electrical power from the same source as that which energises the sign lighting, but bypassing the usual timer switch so that, once connected, the transmitter operates continuously. As an alternative, each transmitter may be powered for relatively-short periods by replaceable batteries. Both the mains and the batteries supply energy to a power supply 4 which supplies energy in turn to an encoder 6 and to a transmitter 8. The encoder has a plurality of input lines 10 which may be connected together in a combination which determines the particular encoded signal which passes along an output line 12 to the transmitter so as to modulate its carrier in known fashion.

The transmitter 8 may be of the type which is sold by Quantelec Limited as the ASAP transmitter, which is intended to use a carrier signal at 418 MHz using ASK modulation. It is envisaged that the encoder 6 could provide up to ten different output signals, each of which would modulate the output signal of transmitter 8 in a specific way. Each encoded signal could thus correspond to a specific speed-restriction or traffic hazard. The manner in which the transmitter output is modulated, and the range of different encoded signals, do not form part of the subject-matter of this invention and so are not dealt with herein in any greater detail.

Because of its high frequency, the effective range of transmitter 2 is only about 50 m. In other words, only when a vehicle carrying a receiver 14 comes within this range of a transmitter does the input signal picked up by the vehicle's aerial reach and exceed a threshold value at which it can give rise to a useful output signal. In the illustrated embodiment of the invention, the transmitted signal is received by a miniature superregenerative receiver 16 operating at the carrier frequency of 418 MHz. One example of a suitable receiver is the 'Hybrid Receiver Module' per Quantelec. The receiver 16 is powered by the vehicle battery 18 through a resistor R, which battery also energises a decoder 20 which is supplied by receiver 16 with an encoded input signal which is operated on within the decoder to produce one of the same range of signals which is available to the transmitter. When an appropriate input signal is received, the decoder supplies the respective output signal to an output device (not shown) which may be designed to generate audible signals, such as taped spoken messages, and/or signals which are displayed visually to the driver on a specific display device which is within his range of vision. As the signal generator does not in itself form the subject-matter of this invention, it will not be described herein in any greater detail.

Claims

1. A traffic information system comprising a network of roadside transmitters intended to signal road hazards etc. to the drivers of vehicles equipped with receivers tuned to the wavelength at which the transmitters operate.

2. A system as claimed in claim 1, in which both the transmitter and receiver are adapted to operate at such a high frequency that the transmitter is able to generate an output signal of useful signal strength at ranges up to about 50 m.

3. A system as claimed in claim 2, in which the frequency is 418 MHz.

4. A system as claimed in any preceding claim, in which each transmitter is intended to be powered by a mains electricity supply.

5. A system as claimed in any preceding claim, in which at least some receivers are intended to be powered from the vehicle battery.

6. A system as claimed in any preceding claim, in which at least some of the transmitters have an encoder having several input lines adapted to be connected together in a combination causing the encoder to emit a specific output signal which is used to modulate the transmitter.

7. A traffic information system substantially as described herein with reference to, and as shown in, the accompanying drawing.