Method for predictive rollover prevention of a vehicle

Abstract

A method for preventing a rollover of a vehicle or a tractor-trailer combination in curves, by counteracting a rollover risk of the vehicle by independent regulating interventions, performed without action by a vehicle driver, in a regulation system that actuates the drive and/or the brakes of the vehicle, the method including: capturing the current driving situation and the current load of the vehicle or the tractor-trailer combination as to the current driving position of the vehicle or the tractor-trailer combination, ascertaining a maximum admissible transverse acceleration at the current driving position, at which maximum admissible transverse acceleration the vehicle or the tractor-trailer combination just does not roll over, as to the current driving situation and the current load of the vehicle or the tractor-trailer combination. Also described is a related apparatus for preventing a rollover of a vehicle or a tractor-trailer combination in curves.

Claims

1. A method for preventing a rollover of a vehicle or a tractor-trailer combination in curves, counteracting a rollover risk of the vehicle or the tractor-trailer combination by independent regulating interventions, carried out without action by a vehicle driver, in a regulation system that actuates a drive and/or brakes of the vehicle, the method comprising: a) capturing a current driving situation and a current load of the vehicle or the tractor-trailer combination in relation to a current driving position of the vehicle or the tractor-trailer combination; b) ascertaining a maximum admissible transverse acceleration at the current driving position, at which maximum admissible transverse acceleration the vehicle or the tractor-trailer combination just does not roll over, in relation to the current driving situation and the current load of the vehicle or the tractor-trailer combination; c) obtaining information items about a course of a route, proceeding from the current driving position of the vehicle or the tractor-trailer combination, comprising information items about a curvature profile of the route ahead; d) calculating maximum limit speeds that ensure a rollover-safe passage along the route ahead, in relation to a respective driving position along the route ahead, based on the curvature profile of the route ahead and based on the maximum admissible transverse acceleration according to a following calculation rule: $v_{\max }\left(x\right)=\sqrt{\frac{a_{y\mathrm{maxROP}}}{\left(x\right)}},$ wherein a.sub.y max ROP is the maximum admissible transverse acceleration, wherein v.sub.max(x) is a maximum limit speed for a distance x.sub.1 to x.sub.n, wherein x.sub.1 to x.sub.n are distances along the route, and wherein (x) is the curvature profile; e) calculating longitudinal decelerations that are required to prevent rollover, in relation to the respective driving position along the route ahead, based on the maximum limit speeds and based on a vehicle speed present at the current driving position of the vehicle or the tractor-trailer combination according to the following calculation rule: $a_{\mathrm{xneed}}\left(x\right)=\frac{{v\left(x\right)}_{\max }^2-v_{\mathrm{act}}^2}{2.Math.x},$ wherein a.sub.x need(x) is a longitudinal deceleration to prevent a rollover, wherein v.sub.act is an actual velocity or speed of the vehicle, and wherein x is a distance; f) determining a maximum required deceleration from the longitudinal decelerations that are required to prevent rollover, which are related to the respective driving position along the route ahead:
a.sub.x max need=max(a.sub.x need(x)), wherein a.sub.x need(x) is the longitudinal deceleration to prevent a rollover, and wherein a.sub.x max need is a maximum longitudinal deceleration; and g) regulating, based on the maximum required deceleration, an actual speed of the vehicle or the tractor-trailer combination, depending on a driving position along the route, to the maximum limit speed that was calculated for a relevant driving position so that there only is a regulation of the actual speed for driving positions along the route at which there is a need for the longitudinal deceleration but not the longitudinal acceleration; wherein a radar camera and an evaluation device capture and determine the route ahead, represented by data points x.sub.1 to x.sub.n, wherein evaluation is done with a multi-order polynomial, and wherein based on data obtained about the route ahead, the curvature profile (x) is ascertained in relation to a distance from a current driving position x.sub.act or in relation to a driving position x.sub.i, so that an assigned curvature (x.sub.1), (x.sub.2) . . . (x.sub.n) is calculated for each distance x.sub.1 to x.sub.n from the current driving position x.sub.act according to: $\left(x\right)=\frac{f^{}\left(x\right)}{{\left(1+{f^{}\left(x\right)}^2\right)}^{\frac{3}{2}}},$ so that the course of the route ahead, represented by x.sub.1 to x.sub.n, contains the curvature profile (x) of a roadway; wherein x.sub.act is the current driving position, wherein x.sub.1 to x.sub.n is each distance from the current driving position x.sub.act, wherein f(x) and f(x) are derivatives of f(x), and wherein (x) is the curvature profile.

2. The method of claim 1, wherein a necessary brake force that is required to obtain the maximum required deceleration is calculated based on a mass of the vehicle or the tractor-trailer combination according to:
F.sub.brems=m.sub.Fzg*a.sub.x max need, wherein F.sub.brems is a required brake force, wherein m.sub.Fzg is the mass of the vehicle or the tractor-trailer combination, and wherein a.sub.x max need is the maximum longitudinal deceleration.

3. The method of claim 2, wherein, when the necessary brake force is not able to be applied, or is not able to be applied completely, by an active actuation of a brake of the vehicle or the tractor-trailer combination by the vehicle driver and/or by forces that is able to be traced back to conditions of the route, the required brake force or the component of a brake force that is still missing in relation to the required brake force is produced by actuating, within a meaning of braking, at least one of following vehicle devices without action by the vehicle driver: a continuous service brake device, a motor, a service brake device, a parking brake device.

4. The method of claim 1, wherein capturing the current driving situation of the vehicle or the tractor-trailer combination includes at least one of: an ascertainment of a current speed and/or a current acceleration of the vehicle or the tractor-trailer combination in relation to the current driving position of the vehicle or the tractor-trailer combination.

5. The method of claim 1, wherein obtaining information items about the course of the route ahead, proceeding from the current driving position of the vehicle or the tractor-trailer combination, furthermore contains obtaining information items about a grade, an inclination and/or a coefficient of friction of the route ahead.

6. The method of claim 1, wherein obtaining information items about the course of the route ahead, proceeding from the current driving position of the vehicle or the tractor-trailer combination, is effectuated with onboard devices in relation to the vehicle or the tractor-trailer combination and/or with external data sources.

7. The method of claim 1, wherein characteristics representing risk potentials at assigned driving positions are produced based on the longitudinal decelerations in relation to the respective driving position along the route ahead.

8. The method of claim 7, wherein, if a limit characteristic that represents a certain limit risk potential is already exceeded by a characteristic before reaching the driving position assigned to this characteristic, at least one of the following measures is performed: outputting an acoustic and/or optical warning signal for the vehicle driver, activating collision protection devices, stiffening a suspension of the vehicle or the tractor-trailer combination, increasing a brake pressure in brake cylinders.

9. The method of claim 1, wherein active braking interventions by the vehicle driver are taken into account when determining conditions of the route.

10. The method of claim 1, wherein conditions of the route and/or active braking interventions by the vehicle driver are taken into account when determining required longitudinal decelerations.

11. The method of claim 1, wherein devices that serve to decelerate the vehicle or the tractor-trailer combination are tested in respect of availability of the devices.

12. The method of claim 1, wherein actuations or activations by the vehicle driver of at least one of: a retarder, a brake pedal, a driver assistance system, an accelerator pedal, and/or a differential lock are tested.

13. An apparatus for preventing a rollover of a vehicle or a tractor-trailer combination in curves, comprising: at least one regulation system to actuate a drive and/or brakes of the vehicle, wherein the at least one regulation system counteracts a rollover risk of the vehicle or the tractor-trailer combination by independent regulating interventions, carried out without action by a vehicle driver; wherein the at least one regulation system is configured to perform: a) capturing a current driving situation and a current load of the vehicle or the tractor-trailer combination in relation to a current driving position of the vehicle or the tractor-trailer combination; b) ascertaining a maximum admissible transverse acceleration at the current driving position, at which maximum admissible transverse acceleration the vehicle or the tractor-trailer combination just does not roll over, in relation to the current driving situation and the current load of the vehicle or the tractor-trailer combination; c) obtaining information items about a course of a route, proceeding from the current driving position of the vehicle or the tractor-trailer combination, comprising information items about a curvature profile of the route ahead; d) calculating maximum limit speeds that ensure a rollover-safe passage along the route ahead, in relation to a respective driving position along the route ahead, based on the curvature profile of the route ahead and based on the maximum admissible transverse acceleration according to the following calculation rule: $v_{\max }\left(x\right)=\sqrt{\frac{a_{y\mathrm{maxROP}}}{\left(x\right)}},$ wherein a.sub.y max ROP is the maximum admissible transverse acceleration, wherein v.sub.max(x) is a maximum limit speed for a distance x.sub.1 to x.sub.n, wherein x.sub.1 to x.sub.n are distances along the route, and wherein K(X) is the curvature profile; e) calculating longitudinal decelerations that are required to prevent rollover, in relation to the respective driving position along the route ahead, based on the maximum limit speeds and based on a vehicle speed present at the current driving position of the vehicle or the tractor-trailer combination according to the following calculation rule: $a_{\mathrm{xneed}}\left(x\right)=\frac{{v\left(x\right)}_{\max }^2-v_{\mathrm{act}}^2}{2.Math.x},$ wherein a.sub.x need(x) is a longitudinal deceleration to prevent a rollover, wherein v.sub.act is an actual velocity or speed of the vehicle, and wherein X is a distance; f) determining a maximum required deceleration from the longitudinal decelerations that are required to prevent rollover, which are related to the respective driving position along the route ahead:
a.sub.x max need=max(a.sub.x need(x)), wherein a.sub.x need(x) is the longitudinal deceleration to prevent a rollover, and wherein a.sub.x max need is a maximum longitudinal deceleration; and g) regulating, based on the maximum required deceleration, an actual speed of the vehicle or the tractor-trailer combination, depending on a driving position along the route, to the maximum limit speed that was calculated for a relevant driving position so that there only is a regulation of the actual speed for driving positions along the route at which there is a need for the longitudinal deceleration but not the longitudinal acceleration; wherein a radar camera and an evaluation device capture and determine the route ahead, represented by data points x.sub.1 to x.sub.n, wherein evaluation is done with a multi-order polynomial, and wherein based on data obtained about the route ahead, the curvature profile (x) is ascertained in relation to a distance from a current driving position x.sub.act or in relation to a driving position Xi, so that an assigned curvature (x.sub.1), (x.sub.2) . . . (x.sub.n) is calculated for each distance x.sub.1 to x.sub.n from the current driving position x.sub.act according to the following: $\left(x\right)=\frac{f^{}\left(x\right)}{{\left(1+{f^{}\left(x\right)}^2\right)}^{\frac{3}{2}}},$ so that the course of the route ahead, represented by x.sub.1 to x.sub.n, contains the curvature profile (x) of a roadway wherein x.sub.act is the current driving position, wherein x.sub.1 to x.sub.n is each distance from the current driving position x.sub.act, wherein f(x) and f(x) are derivatives of f(x), and wherein (x) is the curvature profile.

14. A vehicle, comprising: an apparatus for preventing a rollover of a vehicle or a tractor-trailer combination in curves, including at least one regulation system to actuate a drive and/or brakes of the vehicle, wherein the at least one regulation system counteracts a rollover risk of the vehicle or the tractor-trailer combination by independent regulating interventions, carried out without action by a vehicle driver; wherein the at least one regulation system is configured to perform: a) capturing a current driving situation and a current load of the vehicle or the tractor-trailer combination in relation to a current driving position of the vehicle or the tractor-trailer combination; b) ascertaining a maximum admissible transverse acceleration at the current driving position, at which maximum admissible transverse acceleration the vehicle or the tractor-trailer combination just does not roll over, in relation to the current driving situation and the current load of the vehicle or the tractor-trailer combination; c) obtaining information items about a course of a route, proceeding from the current driving position of the vehicle or the tractor-trailer combination, comprising information items about a curvature profile of the route ahead; d) calculating maximum limit speeds that ensure a rollover-safe passage along the route ahead, in relation to a respective driving position along the route ahead, based on the curvature profile of the route ahead and based on the maximum admissible transverse acceleration according to the following calculation rule: $v_{\max }\left(x\right)=\sqrt{\frac{a_{y\mathrm{maxROP}}}{\left(x\right)}},$ wherein a.sub.y max ROP is the maximum admissible transverse acceleration, wherein v.sub.max(x) is a maximum limit speed for a distance x.sub.1 to x.sub.n, wherein x.sub.1 to x.sub.n are distances along the route, and wherein (x) is the curvature profile; e) calculating longitudinal decelerations that are required to prevent rollover, in relation to the respective driving position along the route ahead, based on the maximum limit speeds and based on the vehicle speed present at a current driving position of the vehicle or the tractor-trailer combination according to the following calculation rule: $a_{\mathrm{xneed}}\left(x\right)=\frac{{v\left(x\right)}_{\max }^2-v_{\mathrm{act}}^2}{2.Math.x},$ wherein a.sub.x need(x) is a longitudinal deceleration to prevent a rollover, wherein v.sub.act is an actual velocity or speed of the vehicle, and wherein x is a distance ; f) determining a maximum required deceleration from the longitudinal decelerations that are required to prevent rollover, which are related to the respective driving position along the route ahead:
a.sub.x max need=max(a.sub.x need(x)), wherein a.sub.x need(x) is the longitudinal deceleration to prevent a rollover, and wherein a.sub.x max need is a maximum longitudinal deceleration; and g) regulating, based on the maximum required deceleration, an actual speed of the vehicle or the tractor-trailer combination, depending on a driving position along the route, to the maximum limit speed that was calculated for a relevant driving position so that there only is a regulation of the actual speed for driving positions along the route at which there is a need for the longitudinal deceleration but not the longitudinal acceleration; wherein a radar camera and an evaluation device capture and determine the route ahead, represented by data points x.sub.1 to x.sub.n, wherein evaluation is done with a multi-order polynomial, and wherein based on data obtained about the route ahead, the curvature profile (x) is ascertained in relation to a distance from a current driving position x.sub.act or in relation to a driving position x.sub.i, so that an assigned curvature (x.sub.1), (x.sub.2) . . . (x.sub.n) is calculated for each distance x.sub.1 to x.sub.n from the current driving position x.sub.act according to the following: $\left(x\right)=\frac{f^{}\left(x\right)}{{\left(1+{f^{}\left(x\right)}^2\right)}^{\frac{3}{2}}},$ so that the course of the route ahead, represented by x.sub.1 to x.sub.n, contains the curvature profile (x) of a roadway wherein x.sub.act is the current driving position, wherein x.sub.1 to x.sub.n is each distance from the current driving position x.sub.act, wherein f(x) and f(x) are derivatives of f(x),and wherein (x) is the curvature profile.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 shows a schematic illustration of the flow of a method according to the invention in accordance with an exemplary embodiment;

(2) FIG. 2 shows a further schematic illustration of the flow of the method of FIG. 1.

DETAILED DESCRIPTION

(3) FIG. 1 schematically shows a flow of a method for preventing a rollover of a vehicle or a tractor-trailer combination in curves, the method counteracting a rollover risk of the vehicle by way of independent regulating interventions, carried out without action by a vehicle driver, in a regulation system that actuates the drive and/or the brakes of the vehicle.

(4) The vehicle may be a heavy commercial vehicle, in particular a tractor of a tractor-trailer combination with an electropneumatic brake device. By way of example, in the present case, the tractor-trailer combination has a single axle or multi-axle semitrailer (not shown here); however, a drawbar trailer or a number of drawbar trailers or else a single axle or multi-axle center-axle trailer may also be hitched to the tractor. The explanations made below in relation to the method according to the invention apply both to the tractor on its own and to the entire tractor-trailer combination.

(5) Here, a service brake device of the tractor or of the tractor-trailer combination is formed by, for example, an electropneumatic friction brake device in the form of an electronic brake system (EBS), in which the brake pressure is regulated.

(6) In the case of such an electronic brake system (EPS), pressure regulating modules are present on each axle or each wheel, the pressure regulating modules having integrated inlet valves, outlet valves and backup valves and having pressure sensors for capturing the actual brake pressure and having a local electronic controller or brake pressure regulator for matching the actual brake pressures to the setpoint brake pressures according to the respective braking requirement. The construction and function of such pressure regulating modules are sufficiently well known and will therefore not be discussed in any more detail here.

(7) The electronic brake system (EBS) of the tractor furthermore contains a brake-slip control (ABS), the ABS control routines of which may be integrated into a central electronic EBS brake controller. Furthermore, in the electronic brake system (EBS) here, there may be a traction control system (ASR), an electronic stability program (ESP) with a roll stability program (RSP) or a roll stability control (RSC) as a partial function, which attempts to prevent the tractor or the tractor-trailer combination from rolling over, particularly during cornering, wherein the control routines in this respect are likewise implemented in the central brake controller.

(8) Within the scope of the roll stability program (RSP), the current driving situation and the current load of the tractor or the tractor-trailer combination may be captured in relation to a current driving position x.sub.act of the tractor or the tractor-trailer combination. By way of example, the current driving situation contains the current speed v.sub.act and/or the current acceleration acct of the tractor or the tractor-trailer combination in relation to the current driving position x.sub.act. In FIG. 1, this step is symbolized by the Analysis of the vehicle state box. The Analysis of the vehicle state furthermore also contains, for example, the distribution of the load/mass to the front/back and an ascertainment of the position of the center of mass, in particular the center-of-mass height. Furthermore, this analysis may also contain testing the availability of devices and functions that can ensure a deceleration of the tractor or the tractor-trailer combination, such as the service brake device, the parking brake device and/or a retarder, for example. Furthermore, this analysis may also contain a test of activations and actuations of devices by the vehicle driver, such as e.g. a retarder activity, a brake pedal position, an activation of various comfort functions (ACC, cruise control), an accelerator pedal position, a differential lock.

(9) Furthermore, a maximum admissible transverse acceleration a.sub.y max ROP at the current driving position x.sub.act may be ascertained within the scope of the roll stability program (RSP), at which maximum admissible transverse acceleration the vehicle or the tractor-trailer combination just does not roll over, to be precise in relation to the current driving situation and the current load of the tractor or the tractor-trailer combination. In FIG. 1, this step is characterized by the Calculating the maximum admissible transverse acceleration box.

(10) In parallel therewith, or therebefore or thereafter in time, information items about the course of a route x.sub.1 to x.sub.n ahead are captured, proceeding from a current driving position x.sub.act of the vehicle or the tractor-trailer combination, the information items, in particular, comprising information items about the curvature profile (x) of the route x.sub.1 to x.sub.n ahead. In FIG. 1, this step is symbolized by the Information about the course of the roadway ahead and the box adjoining this to the right.

(11) The route ahead (Path of the road markers) is characterized here by n nodes x.sub.i (i=1 to n, road markers), for example, as shown in FIG. 2, in particular. The character x or the characters x.sub.1, x.sub.2, x.sub.3, . . . x.sub.n represents/represent the distance x of a driving position along the route x.sub.1 to x.sub.n ahead from the current driving position x.sub.act, as illustrated in the Distance x box in FIG. 2.

(12) Here, the assumption is made that the route x.sub.1 to x.sub.n ahead is in a plane. However, in addition, the vertical course of the route ahead can also be captured. By way of example, in this diagram, the current driving position x.sub.act of the tractor is at the start of the diagram at the time t=0, and so, proceeding from the current driving position x.sub.act, the tractor assumes the nodes x.sub.1 to x.sub.n or the distances x.sub.1 to x.sub.n from the current driving position x.sub.act with increasing time t. Here, the last distance x.sub.n marks the last node, the data of which are known or are able to be obtained.

(13) By way of example, the tractor has an onboard radar camera with a dedicated evaluation device, by which the route x.sub.1 to x.sub.n ahead is captured. Here, the evaluation may be effectuated with the aid of a third order polynomial:
f(x)=C.sub.0+C.sub.1.Math.x+C.sub.2x.sup.2+C.sub.3x.sup.3

(14) On the basis of the data obtained about the route x.sub.1 to x.sub.n ahead, the curvature profile thereofcurvature or (x)is ascertained in relation to the distance from the current driving position x.sub.act or in relation to the driving position x.sub.i. Consequently, the assigned curvature (x.sub.1), (x.sub.2) . . . (x.sub.n) is calculated in this step for each distance x.sub.1 to x.sub.n from the current driving position x.sub.act according to the following calculation rule:

(15) $\left(x\right)=\frac{f^{}\left(x\right)}{{\left(1+{f^{}\left(x\right)}^2\right)}^{\frac{3}{2}}}$

(16) The information items about the course of a route x.sub.1 to x.sub.n ahead therefore contain the curvature profile (x) of the roadway. Moreover, the following variables contribute to improve and clarify the course of the route x.sub.1 to x.sub.n ahead: the grade, the (lateral) inclination and the coefficient of friction of the route or the roadway.

(17) The information about the course of a route x.sub.1 to x.sub.n ahead can be provided by the radar camera directly on board of the tractor, as may be in this case, and/or can be obtained from data transmitted from external devices. By way of example, these data can be provided or transmitted from the following systems: radar systems, camera systems, lidar systems, ultrasound systems, car-to-car communication systems, car-to-cloud-to-car communication systems, road-to-car communication systems, navigation systems (electronic map material).

(18) This is followed by the step of calculating maximum limit speeds v.sub.max(x) that ensure a rollover-safe passage along the route x.sub.1, x.sub.n ahead, in relation to the respective driving position x along the route x.sub.1, x.sub.n ahead, on the basis of the curvature profile (x) of the route x.sub.1, x.sub.n ahead and on the basis of the maximum admissible transverse acceleration a.sub.y max ROP according to the following calculation rule:

(19) $v_{\max }\left(x\right)=\sqrt{\frac{a_{y\max \mathrm{ROP}}}{\left(x\right)}}$

(20) This step is symbolized by the Calculation of limit speeds box in FIG. 1 and by the Maximal speed limit to not roll over box in FIG. 2. Consequently, the assigned limit speed v.sub.max(x.sub.1), v.sub.max(x.sub.2), v.sub.max(x.sub.n) for each distance x.sub.1 to x.sub.n is calculated in this step. Consequently, the limit speeds v.sub.max(x.sub.1), v.sub.max(x.sub.2), . . . v.sub.max(x.sub.n) that ensure a rollover-safe passage of the route x.sub.1, x.sub.n ahead are calculated. The curvatures (x) to be driven are known from the previously transmitted or provided information items about the route x.sub.1, x.sub.n ahead or they were ascertained. The maximum admissible transverse acceleration a.sub.y max ROP was determined by analyzing the current driving situation and the current load of the tractor or the tractor-trailer combination. The admissible transverse acceleration a.sub.y max ROP describes the transverse acceleration at which the tractor or the tractor-trailer combination just does not roll over under the current driving situation (speed, longitudinal acceleration) and the current load. The ascertained admissable transverse acceleration a.sub.y max ROP may be related to the roadway information items (e.g. grade, lateral inclination) and the current activities of the vehicle driver. Then, the maximum limit speed v.sub.max(x) is calculated from the ascertained admissible transverse acceleration a.sub.y max ROP and the curvatures (x) to be driven.

(21) In the next step, which is symbolized by the Calculating the required longitudinal acceleration box in FIG. 1 and by the Needed deceleration to reach max speed limit box in FIG. 2, longitudinal decelerations a.sub.x need(x) that are required to prevent rollover, in relation to the respective driving position or distance x along the route x.sub.1, x.sub.n ahead, are calculated on the basis of the maximum limit speeds v.sub.max(x) and on the basis of the vehicle speed v.sub.act present at the current driving position x.sub.act of the vehicle or the tractor-trailer combination according to the following calculation rule:

(22) $a_{x\mathrm{need}}\left(x\right)=\frac{{v\left(x\right)}_{\max }^2-v_{\mathrm{act}}^2}{2.Math.x}$

(23) Consequently, the longitudinal decelerations a.sub.x need(x) that are required to prevent rollover are length-wise decelerations. Consequently, the assigned longitudinal deceleration a.sub.x need(x.sub.1) . . . a.sub.x need(x.sub.n) that is required to prevent rollover is calculated for each distance x.sub.1 to x.sub.n from the current driving position x.sub.act in this step.

(24) In the next step, which is not shown in the figures, a maximum required deceleration a.sub.x max needed is determined from the longitudinal decelerations a.sub.x need(x) that are required to prevent rollover, which are related to the respective driving position or distance x along the route (x.sub.1, x.sub.n) ahead:
a.sub.x max need=max(a.sub.x need(x))

(25) In the next step, there is a regulation, on the basis of the maximum required deceleration a.sub.x max needed, of the actual speed of the vehicle or the tractor-trailer combination, depending on the driving position or distance x along the route x.sub.1, x.sub.n, to the maximum limit speed v.sub.max(x) that was calculated for the relevant driving position or distance x in such a way that there only is a regulation of the actual speed for the driving positions or distances x along the route x.sub.1, x.sub.n at which there is a need for a longitudinal deceleration but no longitudinal acceleration. The background of this procedure is that no positive acceleration should be exerted on the tractor or the tractor-trailer combination without action by the vehicle driver; instead, all that should be carried out is a deceleration (negative acceleration) where necessary. Therefore, if the ascertained longitudinal acceleration is not a deceleration, it is not considered any further.

(26) Furthermore, characteristics representing risk potentials at assigned driving positions x may be produced on the basis of the longitudinal decelerations a.sub.x need(x) in relation to the respective driving position or distance x along the route x.sub.1, x.sub.n ahead.

(27) In so doing, particularly if a limit characteristic that represents a certain limit risk potential is already exceeded by a characteristic before reaching the driving position x assigned to this characteristic, at least one of the following measures can be performed: outputting an acoustic and/or optical warning signal for the vehicle driver, activating collision protection devices, stiffening the suspension of the vehicle or the tractor-trailer combination, increasing the brake pressure in brake cylinders.

(28) In FIG. 1, this step is symbolized by the Evaluating the risk potential and regulating to a limit speed block.

(29) In order to implement the maximum required calculated deceleration on the tractor or the tractor-trailer combination, the necessary brake force F.sub.brems for the tractor or the tractor-trailer combination is calculated with the aid of the known vehicle mass:
F.sub.brems=m.sub.Fzg*a.sub.x max need

(30) The necessary brake force F.sub.brems may be related to information items about the roadway (e.g. grade, lateral inclination) and current activities of the vehicle driver.

(31) If the required brake force F.sub.brems is not applied by external circumstances (e.g. grade of the roadway) or by reaction of the driver (e.g. actuation of the brake pedal), the necessary brake force F.sub.brems is realized within the scope of the method by, for example, actuating or activating the following vehicle devices: continuous service brake system (retarder) motor brake (motor torque) braking interventions (overall and individual for each wheel) by service brake and/or parking brake

(32) The results of the calculation of the necessary longitudinal acceleration are used to evaluate the risk potential at the current time of the vehicle. Application parameters render it possible to set the required longitudinal acceleration at which the system should intervene. Thus, for example, the limit speed can be comfortably adjusted merely by an early reduction of the motor torque, or else it can be adjusted very late by a hard brake intervention. This provides the vehicle driver with the option of reacting independently. Any stage between the two aforementioned extremes is conceivable.

(33) If an acute risk potential is assumed, the following measures can be introduced: preparing the brake system and other systems and functions for braking (filling the brake cylinders, firming the chassis, activating collision preparation systems, activating driving dynamics stabilization functions) acoustic/optical feedback to the driver