GB2028546A

GB2028546A - A device for checking the velocity of a motor vehicle

Info

Publication number: GB2028546A
Application number: GB7926265A
Authority: GB
Original assignee: Individual
Current assignee: Individual
Priority date: 1978-07-27
Filing date: 1979-07-27
Publication date: 1980-03-05
Also published as: DE2929902C2; BE877933A; FR2433753A1; FR2433753B1; IT7945722A0; ATA545678A; CH643662A5; GB2028546B; IT1126119B; DE2929902A1; JPS5547452A; CA1142649A; JPS6130692B2; AT360350B

Abstract

A device for checking the velocity of a motor vehicle in relation to existing visibility conditions comprises time measuring means (1) which can be started by a starting switch (2) when a readily distinguished point can be clearly seen on the road in front of the vehicle. As soon as the vehicle passes this point a stopping switch (3) is actuated which stops the time measuring means. The time measuring means (1) thus measures the time interval between the two switch actuations and a calculator (4) calculates the visible distance corresponding to said time interval having regard to the velocity of the vehicle during the interval. This visible distance is compared by the calculator means with the stopping distance corresponding to said velocity. The result of this comparison is indicated by a device (6) which may give a readout of the maximum permissible velocity for the visibility conditions and gives a visible or audible signal if the stopping distance exceeds the visible distance. The value of vehicle velocity may be entered into the calculator manually, or automatically by a coupling to a tachograph. <IMAGE>

Description

SPECIFICAl ION A device for checking the velocity of a motor vehicle The present invention relates to a device for checking the velocity of a motor vehicle, particularly in dependence on the existing visibility conditions.

It is known that a frequent cause of accidents has its origin in the driver underrating the velocity of his motor vehicle or overrating his braking possibilities. There results a bumping accident with an obstacle if the velocity and, respectively, the stopping distance correlated to this velocity was too great to stop in time before this obstacle.

In each vehicle a tachometer is provided for indicating the velocity. However such indication alone is not sufficient because the knowledge of the momentary velocity does not give direct information of the length of the stopping distance.

As a rule, an exact determination of the stopping distance of a motor vehicle is not possible during travelling in view of the constant factors and variable factors to be considered and can, above all, not be made by the driver who has to give his attention to the vehicle and to the events on the road, particularly to the traffic. Most drivers are not in a position to exactly estimate distances when sitting in a moving vehicle. This particularly applies when visibility is poor, for example during night, in fog, bad weather and so on. Any calculations concerning stopping distances and driving velocities are, therefore, as a rule, effected in a retrospective manner after an accident and frequently give results surprising to the persons concerned.

The invention provides a device for checking the velocity of a motor vehicle in dependence on the existing visibility conditions, comprising time measuring means capable of effecting a time measuring operation during a time interval defined by a start time and a stop time, starting means for starting said time measuring means, stopping means for stopping said time measuring means, calculator means operatively connected to said time measuring means and having means for setting the velocity of the motor vehicle driven during said time interval and being capable of calculating the path of travel of the motor vehicle passed during said time interval and for a comparison of this path of travel with the stopping distance corresponding to said velocity of the motor vehicle, and indicating means operatively connected to said calculator means.

Such a device provides the driver or a companion rider with the possibility to easily and quickly and reliably check, without diverting the driver's attention from operating the motor vehicle and, respectively, from the road, whether the driver can stop the vehicle in time in case of an unexpected obstacle in front of him. Further, it is thus possible to derive the maximum velocity of the vehicle which can be driven considering the existing visibility conditions.

With such a device, in the following manner, it can be determined whether the driving velocity and, respectively, the stopping distance correlated thereto is too great.The driver or an assistant driver adjusts on the device the momentary driving velocity. This can, for instance, be manually effected by means of a control device, for example by adjusting knobs. It is, however, more favourable to connect the input of the calculator with an automatic velocity measuring device, for example a tachometer, for adjusting the driving velocity.

Subsequently, the driver or the assistant driver actuates the starting means at exactly that moment in which a striking point located on the road in front of the vehicle can easily be recognized. As soon as the vehicle moves past this point the stopping means will be actuated whereupon the time measuring device measures that time interval which was required to travel along the observed travelling path with the provision that the velocity driven along this travelling path can be considered a constant velocity. The calculator can then calculate the length of the observed travelling path using the equation V L=t 3.6 in which L is the length of the observed travelling path expressed in meters, t is the time interval expressed in seconds and required for travelling along this travelling path and V is the velocity expressed in km/h driven along this travelling path.

If V is to be considered in miles/hour, this equation becomes V L= 1.61 t 3.6 It is within the scope of the present invention to provide the calculator with a circuitry continuously calculating the stopping distance S in meters correlated to the momentary velocity by using, for example, the known rule of thumb S = 0.3 V + (0.1 V)2 (if V is measured in km/h; if V is to be measured in miles/hour, this rule becomes S = 0.3 x 1.61 V+(0.1)V2 x 1.612), comparing this stopping distance with the above mentioned distance L.In the event that S assumes a greater value than L the momentary velocity is too high. If, on the contrary, the value of S is smaller than the value of L, the stopping distance is sufficiently short for the existing visibility conditions and the velocity correlated to the stopping distance is not too high so that the driver can stop his vehicle in time in case of an obstacle in front of him. The result of this comparison can be indicated by the indicating means, for instance by a whistle sound produced when S is greater than L. Another possibility would be an optical indication, for example a red light for S greater than L and a green light for L greater than S.

However, it is frequently desired to give as fast as possible in existing visibility conditions. If S is set equal L, by means of the calculator (or computer) the maximum allowable drive velocity Vmax correlated to the existing visibility conditions can be calculated, without which the measuring process has to be repeated several times in order to stepwisely reach the maximum velocity Vmax mentioned above. Thus the calculator (or computer) can calculate Vmax and this velocity can be indicated by the indicating means. The driver has then only to adjust his velocity to this value Vmax in order that he may drive as fast as allowable considering the existing visibility conditions.This would, however, in some cases require repeated measurement to approximate as near as possible the maximum admissible driving velocity Vmax which corresponds to the existing visibility conditions. To derive an indication of this maximum admissible driving velocity Vmax, the calculator has, according to a preferred embodiment of the invention, an evaluating circuitry which calculates the maximum admissible driving veiocity (in km/h) according to the equation

wherein t is the time interval expressed in seconds between actuating the starting means and actuating the stopping means and VM is the velocity expressed in km/h driving during said time interval.If Vmax has to be measured in miles/hour, this equation becomes

This provides an automatic indication of the maximum admissible driving velocity correlated to the existing visibility conditions, so that the driver need only select a velocity corresponding to this maximum admissible velocity. In view of the calculating time of the calculator being extremely short for the simple calculating operations to be effected, the admissible maximum velocity, which puts the driver into the position to stop in time before an unexpectedly emerging obstacle, is indicated immediately after actuating the stopping switch.

As already mentioned it was up till now a prerequisite that the driving velocity is at least approximately constant during the time measuring operation. To become independent from this prerequisite it is advantageous if a circuitry for determining the average velocity driven during the time measuring operation is provided with the calculator (or computer).

The indication of the momentarily admissible maximum velocity Vmax is, preferably, made in'an optical manner, for example in the manner of a tachometer or as it is usual in pocket calculators.

In the accompanying drawings, embodiments of the invention are shown with reference to block diagrams.

Figure 1 is a circuitry illustrating adjustment of the velocity driven during the measuring interval in a manual manner.

Figure 2 shows a circuitry illustrating automatic adjustment of said velocity by a tachometer and Figure 3 shows a circuitry for considering the average velocity driven during the measuring interval.

Figures 4 and 5 show general views of -embodiments of devices according to the present invention and corresponding to Fig. 1 and 2, respectively.

In the circuitry shown in Figure 1 an electronic time measuring device 1 is provided which can be started by means of a starting switch 2 as soon as the operator can distinctly recognize a striking point located on the travelling path to be travelled upon. As soon as the vehicle travels past this point, the operator actuates a stopping switch 3 interrupting the time measuring process of the time measuring device 1. The time interval measured by the time measuring device 1 is fed to a calculator 4 of electronic type. The velocity driven during the time measuring operation is adjusted on the calculator 4 by means of an adjusting device 5.The calculator calculates the travelling path between the moment of actuating the starting switch 2 and the moment of actuating the stopping switch 3 according to the equation V L=t 3.6 in which L is the travelling path measured in - meters, t is the time measured in seconds and V is the driving velocity of the vehicle in km/h which has been adjusted by means of the adjusting device 5. IfV is to be measured in miles/hour, this equation becomes V L=1.61 t 3.6 The calculator can compare this travelling path L with the stopping distance S evaluated according to the known rule of thumb S = 0.3 V + (0.1 V)2 and being correlated to the momentarily driven velocity V and can give a signal via an indicating device 6 for indicating whether L is greater or smaller than S. It is, however, more favourable if the calculator4 is calculating the maximum admissible driving velocity Vmax as correlated to the existing visibility conditions using the equation

in which t is the time measured in seconds and VM is the average driving velocity in km/h during the measuring operation (adjusted by the adjusting device 5). If Vmax and VM are to be given in miles/hour, this equation reads

This maximum driving velocity Vmax is optically made visible on the indicating device 6 for example in a manner of a tachometer.

The device shown in Figure 2 is similar to that shown in Figure 1. The only difference is a difference in circuitry insofar as the adjustment device 5 for the momentarily driven velocity is not manually actuated but is coupled to the velocity indicating means of the vehicle, for example to the tachometer 7 thereof such that this velocity is automatically fed to calculator 4.

The circuitry shown in Figure 3 differs from the circuitry shown in Figures 1 and 2 only in that for the mentioned checking of the velocity and the stopping distance, respectively, no constant value for the momentarily driven velocity is adjusted on the device but a circuit 8 is fed with signals corresponding to the momentarily driven velocity.

This circuit 8 derives an average value of the velocity during the measuring interval (as defined by actuating the starting switch 2 and the stopping switch 3, respectively) and this average value is fed to the adjusting device 5.-This circuit 8 can be part of the calculator 4. The starting signals and the stopping signals of the starting switch 2 and the stopping switch 3, respectively, are for the mentioned purpose not only fed to the-time measuring device 1 but also fed to the circuit 8 so that this circuit is operative only during the time measuring interval.

The starting switch 2 and the stopping switch 3 can be formed of press buttons but can, if desired, also be acoustic switches which are, for example, actuated by a call of the operator. However, the starting switch and the stopping switch may also be combined in one singie actuating means, for example a depressable key, which gives the start signal when depressed and gives the stop signal when released.

The device can be installed in a portable equipment or be stationarily installed in the motor vehicle itself. A portable device is shown in Figure 4. In a common casing 9 the circuits shown in Figure 1 are arranged. The start switch can be actuated by a press button 10 and the stop switch by a press button 1 both press buttons protruding from the casing so that they can easily be actuated by hand. The velocity of the vehicle can be adjusted by three press buttons 1 2, each one of them being correlated to one decimal value of the velocity. The adjusted value of the velocity can be seen in a window 13. The.calculated value of Vmax can be seen in a further window 1 4. The power supply for the device may be batteries which may also be placed within the casing 9 like in a pocket calculator.

The device according to Figure 5 is suitable for a block diagram of Figure 2. The value of the velocity of the vehicle during the time measuring interval is delivered via a cable 1 5 from the tachometer of the vehicle. Press buttons 1 6, 1 7 and 1 8 are provided to take into account the road conditions. For example, the press button 1 6 may correspond to dry road, the press button 1 7 to wet road and the press button 1 8 to snow covered road. By pressing one of these buttons a suitable correction factor can be inserted into the above mentioned equation S = 0.3 V + (0.1 V)2 for the stopping distance.

Instead of the above mentioned equation for V max an other equation can be used, particularly if one intends to deviate from the usual equation S = 0.3 V + (0.1 V)2 for the stopping distance.

All blocks in the block diagrams of Figures 1-3 are known parse and thus can be built with electronic circuits well known for one skilled in the art. Thus it seems to be superfluous to describe such circuits more in detail.

Claims

1. A device for checking the velocity of a motor vehicle in dependence on the existing visibility conditions, comprising time measuring means capable of effecting a time measuring operation during a time interval defined by a start time and a stop time, starting means for starting said time measuring means, stopping means for stopping said time measuring means, calculator means operatively connected to said time measuring means and having means for setting the velocity of the motor vehicle driven said time interval and being capable of calculating the path of travel of the motor vehicle passed during said time interval and for a comparison of this path of travel with the stopping distance corresponding to said velocity of the motor vehicle, and indicating means operatively connected to said calculator means.

2. A device as claimed in claim 1, wherein said indicating means is capable of indicating a signal correlated to said comparison.

3. A device as claimed in claim 1, wherein said calculator means is also capable of calculating the maximum admissible driving velocity correlated to said comparison, and wherein said indicating means is capable of indicating this maximum' admissible driving velocity.

4. A device as claimed in claim 3, wherein said calculator means is capable of calculating the maximum admissible driving velocity in km/h) according to the equation

wherein t is said time interval expressed in seconds, and VM is the velocity expressed in km/h driven during said time interval.

5. A device as claimed in claim 3, wherein said calculator means is capable of calculafing the maximum admissible driving velocity (in miles/hour) according to the equation

wherein t is said time interval expressed in - seconds, and VM is the velocity expressed in miles/hour driven during said time interval.

6. A device as claimed in claim 1, wherein automatic velocity measuring means is operatively connected to said calculator means for automatically setting the driven velocity.

7. A device as claimed in claim 6, further comprising means for evaluating the average velocity driven during said measuring interval and operatively connected to said calculator means.

8. A device as claimed in claim 3, wherein said indicating means have optical indication means for indicating the maximum admissible velocity.

9. A device for checking the velocity of a motor vehicle in dependence on the existing visibility conditions, substantially as herein described with reference to any one of the embodiments shown in the accompanying drawings.