Vehicle operator advisor system and method

• US 6,498,976 B1
• Filed: 11/01/2000
• Issued: 12/24/2002
• Est. Priority Date: 10/30/2000
• Status: Expired due to Fees

• Current Assignee: Daimler Trucks North America LLC (Mercedes-Benz Group AG)
• Original Assignee: Freightliner Limited (Genesee & Wyoming Incorporated)
• Inventors: Kirn, Christopher L., Moellenhoff, Joerg, Roters, Gerd, Lenz, Thomas, Ruhnau, Gerhard, Ehlbeck, James M.
• Primary Examiner(s): Cuchlinski, Jr., William A.
• Assistant Examiner(s): MARC-COLEMAN, MARTHE Y
• Application Number:
  US09/704,461
• Time in Patent Office: 783 Days
• Field of Search: 701/70, 701/71, 701/72, 701/38, 701/78, 701/79, 701/90, 701/80, 701/81, 701/82, 701/83, 701/91, 303/101, 303/111, 303/107, 303/167, 340/440, 340/438, 340/461, 340/459, 180/197, 180/282
• US Class Current: 701/70
• CPC Class Codes: B60G 17/0162 mainly during a motion involving steering operation, e.g. cornering, overtaking B60G17/0164 takes precedence
• CPC Class Codes: B60G 17/0195 characterised by the regulation being combined with other vehicle control systems conjoint control of vehicle sub-units including control of suspension systems B60W10/22
• CPC Class Codes: B60G 2400/204 Vehicle speed
• CPC Class Codes: B60G 2400/822 Road friction coefficient determination affecting wheel traction
• CPC Class Codes: B60G 2600/02 Retarders, delaying means, dead zones, threshold values, cut-off frequency, timer interruption
• CPC Class Codes: B60G 2800/012 Rolling condition
• CPC Class Codes: B60G 2800/016 Yawing condition
• CPC Class Codes: B60G 2800/215 by applying a braking action on each wheel individually
• CPC Class Codes: B60G 2800/224 automatically, based on dangerous living style
• CPC Class Codes: B60G 2800/242 Obstacle avoidance manoeuvre
• CPC Class Codes: B60G 2800/244 Oversteer
• CPC Class Codes: B60G 2800/70 Estimating or calculating vehicle parameters or state variables
• CPC Class Codes: B60G 2800/704 predicting unorthodox driving conditions for safe or optimal driving
• CPC Class Codes: B60G 2800/9124 Roll-over protection systems, e.g. for warning or control
• CPC Class Codes: B60T 2230/03 Overturn, rollover
• CPC Class Codes: B60T 8/17554 specially adapted for enhancing stability around the vehicles longitudinal axle, i.e. roll-over prevention road vehicle drive control systems for roll-over prevention otherwise than by controlling a particular sub-unit B60W30/04

Abstract

An automatic deceleration control apparatus for a vehicle operates so as to secure appropriate tire grip performance, depending on the conditions of a road surface on which the vehicle runs turning, and restrain excessive rolling of the vehicle body, there by stabilizing the turning behavior of the vehicle at all times. While the vehicle is turning on a high-friction road surface without undergoing haw moment control, a safe vehicle speed is computed within the rollover limit of the vehicle. While the vehicle is turning on a low-friction road surface under haw moment control, on the other hand, a safe vehicle speed that ensures satisfactory tire grip performance is computed in accordance with an estimated road friction coefficient. When the vehicle is about to exceed its safe speed as it turns, it is automatically decelerated to the safe speed or below. Thus, the vehicle can be prevented from spinning, drifting out, or rolling over.

Claims

1. A method of advising a vehicle operator of vehicle driving conditions which create an increased risk of rollover of the vehicle, the method comprising:

determining the mass of the vehicle;

determining a rollover acceleration value which corresponds to the mass of the vehicle;

comparing the rollover acceleration value with a lateral acceleration value which corresponds to the lateral acceleration of the vehicle; and

indicating a rollover risk based upon the comparison.

2. A method according to claim 1 wherein the act of determining the mass of the vehicle comprises the act of estimating the mass of the vehicle.

3. A method according to claim 1 wherein the act of determining the mass of the vehicle comprises estimating the mass of the vehicle at least at selected times when the vehicle is being driven.

4. A method according to claim 1 in which the act of determining the rollover acceleration value comprises assigning a rollover acceleration value based upon a rule set which assigns rollover acceleration values based upon the determined mass of the vehicle.

5. A method according to claim 4 in which the rule set is embodied in at least one look-up table.

6. A method according to claim 4 in which the vehicle is transporting a cargo area, the cargo area being located in a trailer or trailers being towed by the vehicle or being carried by the vehicle, and in which the act of determining the rollover acceleration value comprises assigning a rollover value based upon an assumed manner of loading the cargo area being transported by the vehicle.

7. A method according to claim 1 in which the act of comparing comprises assigning a rollover risk level based upon the extent to which the lateral acceleration value approaches the rollover acceleration value.

8. A method of advising a vehicle operator of vehicle driving conditions which create an increased risk of rollover of the vehicle, the method comprising:

determining the mass of the vehicle;

determining a rollover acceleration value which corresponds to the mass of the vehicle;

comparing the rollover acceleration value with a lateral acceleration value which corresponds to the lateral acceleration of the vehicle;

indicating a rollover risk based upon the comparison; and

in which the indicating act comprises indicating a rollover risk level to the vehicle operator while the vehicle is being driven and following the conclusion of vehicle driving conditions which created the increased risk of rollover to assist in training the driver to learn to avoid the increased rollover risk driving conditions.

9. A method according to claim 8 in which at least two rollover risk levels are indicated to the vehicle operator, the method also including the act of indicating a recommended speed reduction which differs depending upon the rollover risk level to assist in training the driver in how to respond to the driving conditions which led to the indication of the rollover risk level.

10. A method according to claim 8 in which the act of indicating a rollover risk level comprises selectively indicating to a vehicle operator a level of rollover risk in the form of an alphanumeric message.

11. A method according to claim 8 in which the comparing act comprises determining a ratio of the lateral acceleration value to the rollover acceleration value and assigning the rollover risk to a rollover risk category based upon the ratio.

12. A method of advising a vehicle operator of vehicle driving conditions which create an increased risk of rollover of the vehicle, the method comprising:

determining the mass of the vehicle;

determining a rollover acceleration value which corresponds to the mass of the vehicle;

comparing the rollover acceleration value with a lateral acceleration value which corresponds to the lateral acceleration of the vehicle;

indicating a rollover risk based upon the comparison;

in which the comparing act comprises determining a ratio of the lateral acceleration value to the rollover acceleration value and assigning the rollover risk to a rollover risk category based upon the ratio;

wherein there are at least two such rollover risk categories;

the method including the act of determining a proposed reduction in vehicle speed in the event the rollover risk falls into at least one of the at least two categories; and

wherein the indicating act comprises indicating a recommended reduction in speed to the vehicle operator in addition to indicating the rollover risk at a time following the conclusion of driving conditions which led to the rollover risk falling into at least one of the at least two categories.

13. A method according to claim 12 including the act of indicating at least two recommended reductions in speed, a first of such recommended reductions in speed being indicated in the event the rollover risk falls into one of the at least two categories and the second recommended reduction in speed being indicated in the event the rollover risk falls into another of the at least two categories.

14. A method according to claim 13 in which the magnitude of the speed reduction set forth in the first and second speed reduction recommendations is variable.

15. A method according to claim 14 wherein there are at least three such categories of rollover risk which are indicated and wherein no recommended reduction in speed is made in the event the risk falls into a first of the at least three categories, the first category corresponding to a lower risk than the other categories.

16. A method according to claim 15 in which the indicating act comprises providing the vehicle operator with an alphanumeric message indicating the category of rollover risk at a time following the conclusion of driving conditions which resulted in the indication of rollover risk.

17. A method according to claim 16 including the act of flashing the alphanumeric message at a first rate of flashing if the rollover risk is in one category and at a second rate of flashing which is greater than the first rate of flashing in the event the rollover risk is in another category which corresponds to a rollover risk which is higher than the first category of rollover risk.

18. A method according to claim 17 including the act of providing an audible signal which varies depending upon the category of rollover risk.

19. A method of advising a vehicle operator of vehicle driving conditions which create an increased risk of rollover of the vehicle, the method comprising:

determining the mass of the vehicle;

determining a rollover acceleration value which corresponds to the mass of the vehicle;

comparing the rollover acceleration value with a lateral acceleration value which corresponds to the lateral acceleration of the vehicle;

indicating a rollover risk based upon the comparison; and

wherein the comparing act comprises generating a rollover risk score from a ratio of the lateral acceleration value to the rollover acceleration value.

20. A method of advising a vehicle operator of vehicle driving conditions which create an increased risk of rollover of the vehicle, the method comprising:

determining the mass of the vehicle;

determining a rollover acceleration value which corresponds to the mass of the vehicle;

comparing the rollover acceleration value with a lateral acceleration value which corresponds to the lateral acceleration of the vehicle;

indicating a rollover risk based upon the comparison;

in which the vehicle has an automatically modulated braking system which controls the braking at least at selected wheels of the vehicle, the control of braking at a wheel being modulated under certain wheel slip conditions, the automatically modulated braking system producing first signals indicating the modulation of the wheels, the automatically modulated braking system also producing second signals which indicate the rate at which the acceleration of the vehicle is taking place, the method comprising;

determining from the first signals whether one or more wheels is being modulated by the automatically modulated braking system, such condition being a wheel modulation hard-braking event;

determining from the second signals whether braking is producing deceleration at a rate which exceeds a first deceleration rate for a time which exceeds a first time period, such condition being a rapid deceleration hard-braking event;

indicating a first level of hard-braking event in the event a wheel modulation hard-braking event is detected without the detection of a rapid deceleration hard-braking event;

indicating a second level of hard-braking event in the event a rapid deceleration hard-braking event is determined without the occurrence of a wheel modulation hard-braking event; and

indicating a third level of hard-braking event in the event both the modulation wheel hard-braking event and rapid deceleration hard-braking events have occurred.

21. A method according to claim 20 in which the acts of indicating the occurrence of first, second and third hard-braking event levels is accomplished after braking conditions have concluded which led to the determination of a hard-braking event, whereby the indication is useful in training the vehicle operator to avoid driving conditions which lead to hard-braking events.

22. A method according to claim 20 including the act of determining the commencement of a hard-braking event upon a determination that at least one of the first, second and third hard-braking event levels have been reached and determining the end of a hard-braking event when all of the first, second and third levels are no longer present;

and

indicating to the vehicle operator the hard-braking event level that was determined to exist during the hard-braking event, the act of indicating taking place following the end of the hard-braking event.

23. A method according to claim 22 in which the act of indicating the hard-braking event level is blocked for events in which the lateral acceleration value exceeds a predetermined threshold.

24. A method according to claim 22 in which a priority is assigned to the indication of rollover risk and hard-braking events.

25. A method according claim 24 in which the indicating act includes the act of selectively indicating the number of hard-braking event and number of rollover risk events that have taken place during a vehicle trip, the rollover risk events corresponding to events in which rollover risk exceeded a rollover threshold.

26. A method according to claim 25 in which the indicating act includes the act of indicating the number of rollover risk events that have been indicated and the number of hard-braking events that have been indicated during a segment or leg of a vehicle trip.

27. A method of advising a vehicle operator of the occurrence of hard-braking events, the vehicle having an automatically modulated braking system which controls the braking at least at selected wheels of the vehicle, the control of braking at a wheel being modulated under certain wheel slip conditions, the automatically modulated braking system producing first signals upon modulation of the wheels of the vehicle, the automatically modulated braking system also producing second signals which indicate the rate at which the acceleration of the vehicle is taking place, the method comprising:

determining from the first signals whether one or more wheels is being modulated by the automatically modulated braking system, the modulation of at least one wheel being a wheel modulation hard-braking event;

determining from the second signals whether braking is producing deceleration at a rate which exceeds a first deceleration rate for a time which exceeds a first time to thereby determine the occurrence of a rapid deceleration hard-braking event;

indicating a first level of hard-braking event in the event a wheel modulation hard-braking event is detected without the detection of a rapid deceleration hard-braking event;

indicating a second level of hard-braking event in the event a rapid deceleration hard-braking event is determined without the occurrence of a wheel modulation hard-braking event; and

indicating a third level of hard-braking event in the event both the modulation wheel hard-braking event and rapid deceleration hard-braking events have occurred.

28. A method according to claim 27 in which the acts of indicating the occurrence of first, second and third hard-braking event levels is accomplished after braking conditions have concluded which led to the determination of a hard-braking event, whereby the indication is useful in training the vehicle operator to avoid driving conditions which lead to hard-braking events.

29. A method according to claim 27 including the act of determining the commencement of a hard-braking event upon a determination that at least one of the first, second and third hard-braking event levels have been reached and determining the end of a hard-braking event when all of the first, second and third levels are no longer present;

and

indicating to the vehicle operator the hard-braking event level that was determined to exist during the time of the event, the act of indicating taking place following the end of the hard-braking event.

30. A method according to claim 29 in which the act of indicating the hard-braking event level is blocked in the event the lateral acceleration value exceeds a predetermined threshold.

31. A method according to claim 30 in which a priority is assigned to the hard-braking events, with the third level being higher than the second level and the second level being higher than the first level.

32. A method according claim 30 in which the indicating act comprises the act of selectively indicating the number of hard-braking events that have taken place during a vehicle trip.

33. A method of advising a vehicle operator of a course of action upon the occurrence of conditions which create an increased risk of rollover of the vehicle, the method comprising:

evaluating the risk of vehicle rollover as a vehicle is being driven;

determining a reduction in vehicle speed recommendation which varies with the evaluated risk of vehicle rollover;

indicating the recommended reduction in speed recommendation to the vehicle operator;

in which the recommended reduction in speed recommendation is indicated to the vehicle operator following the conclusion of driving conditions which led to the risk of vehicle rollover being at least at a first threshold value;

in which the act of evaluating the risk of a vehicle rollover includes the act of assigning at least two risk categories based on the evaluated risk of vehicle rollover; and

wherein

the act of determining a reduction in speed recommendation comprises varying the reduction in speed recommendation depending upon the category in which the evaluated risk falls.

34. A method according to claim 33 wherein the recommended speed reductions are of specified speed magnitude reductions in miles per hour or kilometers per hour.

35. A method according to claim 34 wherein there are at least three risk categories of higher to lower risk;

wherein in the event the evaluation of the risk of vehicle rollover determines a rollover risk of the highest risk category, a first reduction in vehicle speed recommendation is determined; and

wherein in the event the evaluation of the risk of vehicle rollover determines a rollover risk of a category of risk which is lower than the highest risk category, a second reduction in vehicle speed recommendation is determined which is lower speed reduction recommendation made by the first reduction in vehicle speed recommendation.

36. A method according to claim 34 wherein the magnitude of the speed reduction set forth in the speed reduction recommendation is variable.

37. A method according to claim 36 in which the act of indicating the recommended reduction in speed recommendation comprises displaying a recommended speed reduction in alphanumeric characters.

38. A method according to claim 37 including the act of displaying a message in alphanumeric characters which corresponds to the category of rollover risk.

39. A method of advising a vehicle operator of vehicle driving conditions which create an increased risk of rollover of the vehicle, the method comprising:

determining the mass of the vehicle by repeatedly estimating the mass of the vehicle while the vehicle is being driven;

determining a rollover acceleration threshold value based upon a rule set which assigns rollover acceleration threshold values based upon the determined mass of the vehicle, the rule set being embodied in at least one look-up table;

wherein the vehicle is transporting a cargo area, the cargo area being located in a tailer or trailers being towed by the vehicle or being carried by the vehicle, and in which the act of determining the rollover acceleration threshold value comprises assigning a rollover threshold values to the lookup table based upon an assumed manner of loading the cargo area being transported by the vehicle;

determining a lateral acceleration value which corresponds to the lateral acceleration of the vehicle;

comparing the rollover threshold value and the lateral acceleration value and assigning a rollover risk based upon the extent to which the lateral acceleration value approaches the rollover acceleration threshold value;

wherein at least two rollover risk levels are assigned;

selectively indicating the rollover risk level to the vehicle operator, selectively indicating to the vehicle operator a recommended speed reduction of a first amount for a rollover risk at a first level and a recommended speed reduction of a second amount for a rollover risk at a second level which differs from the first level, the selective indications being made to the vehicle operator as rollover advisories after the end of driving conditions which resulted in the assigning of the rollover risk levels;

the act of selectively indicating comprising flashing a rollover risk message at a first rate of flashing if the rollover risk is of one level and at a second rate of flashing which is greater than the first rate of flashing in the event the rollover risk is at a second level which is greater than the first level;

wherein the vehicle has an automatically modulating braking system which controls the braking at least at selected wheels of the vehicle, the control of braking at a wheel being modulated by the automatically modulating braking system under certain wheel slip conditions, the automated braking system producing modulation braking signals in response to modulation of braking of wheels by the automated braking system, the automated braking system also providing rapid deceleration signals which indicate the rate at which the deceleration of the vehicle is taking place, the method comprising the acts of determining from the modulation braking signals whether one or more wheels is being modulated by the automated braking system, which corresponds to a wheel modulation hard-braking event and determining from the rapid deceleration braking signals whether braking is producing deceleration at a rate which exceeds a first rate for at least a first time period to thereby indicate a rapid deceleration hard-braking event;

determining a first level of hard-braking event in the event a wheel modulation braking event is detected without the detection of a rapid deceleration braking event;

determining a second level of hard-braking event in the event a rapid deceleration hard-braking event is detected without the occurrence of a wheel modulation hard-braking event;

determining a third level of hard-braking event in the event both the modulation wheel hard-braking event and rapid deceleration hard-braking event have occurred;

determining the commencement of individual hard-braking events upon a determination that at least one of the first, second and third hard-braking event levels have been reached and determining the ending of the individual hard-braking events when all of the first, second and third levels are determined to no longer be taking place;

selectively indicating to the vehicle operator the hard-braking event level that was determined to exist during individual hard-braking events, the third level being higher than the second level and the second level being higher than the first level, the hard-braking event level for each individual hard-braking event being indicated following the end of the individual hard-braking event;

blocking the indicating of the hard-braking event level for an individual hard-braking event if the lateral acceleration value exceeds a predetermined threshold; and

wherein the indicating act comprises the act of selectively indicating the number of hard-braking events and number of rollover advisory events that have been indicated during a vehicle trip and during a segment of the trip.

40. An apparatus for advising a vehicle operator of vehicle driving conditions which create an increased risk of rollover of the vehicle, the apparatus comprising:

a vehicle mass determinator operable to determine the mass of a vehicle and to provide a mass indicating signal which corresponds to an estimate of the mass of the vehicle;

an acceleration estimator coupled to the vehicle mass determinator and responsive to the mass indicating signal to produce a critical acceleration estimate which is related to a critical lateral acceleration of the vehicle at which the risk of vehicle rollover is increased;

a vehicle lateral acceleration determinator operable to provide a lateral acceleration signal corresponding to the lateral acceleration of the vehicle;

a roll stability advisor coupled to the acceleration estimator and to the vehicle lateral acceleration determinator so as to receive the lateral acceleration signal and the critical acceleration estimate signal, the roll stability advisor being operable to compare the lateral acceleration signal and critical acceleration estimate signal to produce a rollover risk output signal corresponding to the result of the comparison with the rollover risk being greater as the lateral acceleration approaches the critical lateral acceleration; and

an indicator operable to selectively indicate the rollover risk in response to the rollover risk output signal.

41. An apparatus according to claim 40 in which the roll stability advisor is operable to produce a rollover risk output signal indicative of the rollover risk exceeding a threshold, the indicator being operable to indicate rollover risks which exceed the threshold to a vehicle operator following the end of driving conditions which led to the rollover risk exceeding the threshold, whereby the vehicle operator is provided with feedback concerning driving conditions which result in increased rollover risks.

42. An apparatus according to claim 40 wherein the roll stability advisor is operable to compare the vehicle lateral acceleration signal and the critical acceleration estimate signal and to produce a rollover risk output signal indicative of a high rollover risk in the event the lateral acceleration is near enough to the critical acceleration estimate for a predetermined time period, the roll stability advisor being operable to produce a rollover risk output signal indicative of at least one of a plurality of levels of rollover risk depending upon the closeness of the lateral acceleration of the vehicle to the critical acceleration estimate.

43. An apparatus according to claim 40 wherein the acceleration estimator comprises a lookup table from which a critical acceleration estimate is found in response to the determined vehicle mass.

44. An apparatus for advising a vehicle operator of vehicle driving conditions which create an increased risk of rollover of the vehicle, the apparatus comprising:

a vehicle mass determinator operable to determine the mass of a vehicle and to provide a mass indicating signal which corresponds to an estimate of the mass of the vehicle;

an acceleration estimator coupled to the vehicle mass determinator and responsive to the mass indicating signal to produce a critical acceleration estimate which is related to a critical lateral acceleration of the vehicle at which the risk of vehicle rollover is increased;

a vehicle lateral acceleration determinator operable to provide a lateral acceleration signal corresponding to the lateral acceleration of the vehicle;

a roll stability advisor coupled to the acceleration estimator and to the vehicle lateral acceleration determinator so as to receive the lateral acceleration signal and the critical acceleration estimate signal, the roll stability advisor being operable to compare the lateral acceleration signal and critical acceleration estimate signal to produce a rollover risk output signal corresponding to the result of the comparison with the rollover risk being greater as the lateral acceleration approaches the critical lateral acceleration; and

an indicator operable to selectively indicate the rollover risk in response to the rollover risk output signal;

wherein the roll stability advisor is operable to compare the vehicle lateral acceleration signal and the critical acceleration estimate signal and to produce a rollover risk output signal indicative of a high rollover risk in the event the lateral acceleration is near enough to the critical acceleration estimate for a predetermined time period, the roll stability advisor being operable to produce a rollover risk output signal indicative of at least one of a plurality of levels of rollover risk depending upon the closeness of the lateral acceleration of the vehicle to the critical acceleration estimate; and

in which the roll stability advisor is operable to determine a ratio of the lateral acceleration signal to the critical acceleration estimate signal and to compare this ratio with plural risk threshold levels, the roll stability advisor being operable to require the ratio to be above at least one of the plural risk threshold levels for a time period if conditions are such that a rollover risk is to be indicated.

45. An apparatus according to claim 44 in which the roll stability advisor is operable to produce a vehicle speed reduction recommendation of a magnitude which varies with the determined risk threshold level of rollover risk that is indicated by the roll stability advisor, the speed reduction recommendation being produced after the end of driving conditions which led to indicate the existence of a rollover risk of a magnitude which is at least at one of the risk threshold levels.

46. An apparatus according to claim 45 wherein the indicator is operable alternately indicate the rollover risk level and the speed reduction recommendations.

47. An apparatus for advising a vehicle operator of vehicle driving conditions which create an increased risk of rollover of the vehicle, the apparatus comprising:

a vehicle mass determinator operable to determine the mass of a vehicle and to provide a mass indicating signal which corresponds to an estimate of the mass of the vehicle;

an acceleration estimator coupled to the vehicle mass determinator and responsive to the mass indicating signal to produce a critical acceleration estimate which is related to a critical lateral acceleration of the vehicle at which the risk of vehicle rollover is increased;

a vehicle lateral acceleration determinator operable to provide a lateral acceleration signal corresponding to the lateral acceleration of the vehicle;

a roll stability advisor coupled to the acceleration estimator and to the vehicle lateral acceleration determinator so as to receive the lateral acceleration signal and the critical acceleration estimate signal, the roll stability advisor being operable to compare the lateral acceleration signal and critical acceleration estimate signal to produce a rollover risk output signal corresponding to the result of the comparison with the rollover risk being greater as the lateral acceleration approaches the critical lateral acceleration; and

an indicator operable to selectively indicate the rollover risk in response to the rollover risk output signal;

in which the vehicle includes an automatically modulated braking system which produces second signals indicating the deceleration of the vehicle and first signals whenever any vehicle wheels beings controlled by the automatically modulated braking system are being modulated;

a hard-braking event detector operable in response to the first signals to produce a first hard-braking event signal in the event the automatically modulated braking system is modulating at least one wheel of the vehicle, the first hard-braking event signal indicating a first hard-braking event level;

the hard-braking event detector also being operable to produce a second hard-braking event signal in response to the second signals in the event the automatically modulated braking system indicates deceleration of the vehicle at least at a first rate and at least for a first time period without at least one wheel being modulated by the automatically modulated braking system, the second hard-braking event signal indicating a second hard-braking event level;

the hard-braking event detector also being operable to produce a third hard-braking event signal corresponding to a third hard-braking event level in response to the first and second signals and in the event both the first and second hard-braking event levels are reached during a braking event, the braking event commencing upon the detection of any of the first and second hard-braking event signals and ending upon the end of both of the first and second hard-braking event signals; and

wherein the indicator is operable to selectively indicate the hard-braking event level that has been detected.

48. An apparatus according to claim 47 in which the hard-braking event detector is coupled to the lateral acceleration determinator to receive the lateral acceleration signal, and wherein the hard-braking event detector is operable to block the indication of a hard-braking event level in the event the vehicle lateral acceleration as indicated by the lateral acceleration signal exceeds an acceleration threshold.

49. An apparatus according to claim 48 in which a hard-braking event level is indicated following the end of the hard-braking event which resulted in the determination of the hard-braking event level.

50. A vehicle display responsive to input signals to produce alphanumeric messages corresponding to the vehicle being operated under conditions which increase the risk of vehicle rollover, the messages including at least one rollover risk message indicating the level of rollover risk and at least one speed reduction message recommending a level at which vehicle speed should be reduced;

and a data input device, the apparatus being responsive to an acknowledgement signal entered by the data input device to terminate the messages.

51. A vehicle display responsive to input signals to produce alphanumeric messages corresponding to the vehicle being operated under conditions which increase the risk of vehicle rollover, the messages including at least one rollover risk message indicating the level of rollover risk and at least one speed reduction message recommending a level at which vehicle speed should be reduced;

and

in which there are at least two such rollover risk messages, one indicating a rollover risk at a first level and a second indicating a rollover risk at a second level and wherein there are at least two such speed reduction messages, the speed reduction messages recommending different magnitudes of speed reduction with a higher recommended magnitude of speed reduction corresponding to the higher rollover risk message and the lower recommended magnitude of speed reduction corresponding to the lower of roller risk.

52. A display according to claim 51 in which the rollover risk and speed reduction messages are alternately displayed.

53. An apparatus according to claim 52 in which the rollover risk messages of a higher level are visually and auditorially distinguished from rollover risk messages of a lower level.

54. An apparatus according to claim 52 including a data input device, the apparatus being responsive to an acknowledgement signal entered by the data input device to terminate the messages.

55. An apparatus according to claim 54 in which the data input device has a key with a first symbol, the messages also containing the first symbol, whereby the acknowledgement is entered by the key having the first symbol thereon.

56. An apparatus for advising a vehicle operator of vehicle driving conditions which create an increased risk of rollover of the vehicle, the apparatus comprising:

means for generating a first signal corresponding to a critical acceleration estimate, the critical acceleration estimate being determined from an estimated mass of the vehicle and being based on a set of rules;

means for producing a second signal corresponding to the vehicle lateral acceleration;

roll stability advisor means for comparing the first and second signals and for producing an output signal indicative of the rollover risk; and

indicator means for indicating the rollover risk in response to the roll stability advisor output signal.

57. An apparatus according to claim 56 in which the roll stability advisor also comprises means for selectively providing an output signal indicating recommended speed reductions and wherein the indicator means selectively indicates the rollover risk and speed reduction recommendations to a vehicle operator.

58. An apparatus for advising a vehicle operator of vehicle driving conditions which create an increased risk of rollover of the vehicle, the apparatus comprising:

means for generating a first signal corresponding to a critical acceleration estimate, the critical acceleration estimate being determined from an estimated mass of the vehicle and being based on a set of rules;

means for producing a second signal corresponding to the vehicle lateral acceleration;

roll stability advisor means for comparing the first and second signals and for producing an output signal indicative of the rollover risk; and

indicator means for indicating the rollover risk in response to the roll stability advisor output signal;

in which the roll stability advisor also comprises means for selectively providing an output signal indicating recommended speed reductions and wherein the indicator means selectively indicates the rollover risk and speed reduction recommendations to a vehicle operator; and

also comprising hard-braking event detector means for determining whether hard-braking events have occurred and for producing an output signal indicative of the level of hard-braking event which has occurred, and wherein the indicator means selectively indicates the existence of a hard-braking event and the level of the hard-braking event.

59. In a vehicle which includes an automatically modulated braking system which produces second signals indicating the deceleration of the vehicle and first signals whenever any vehicle wheels beings controlled by the automatically modulated braking system are being modulated, an apparatus for detecting and indicating hard-braking events comprising:

a hard-braking event detector operable in response to the first signals to produce a first hard-braking event signal in the event the automatically modulated braking system is modulating at least one wheel of the vehicle, the first hard-braking event signal indicating a first hard-braking event level;

the hard-braking event detector also being operable to produce a second hard-braking event signal corresponding to a second hard-braking event level in response to the second signals in the event the automatically modulated braking system indicates deceleration of the vehicle at least at a first rate and at least for a first time period without at least one wheel being modulated by the automatically modulated braking system;

the hard-braking event detector also being operable to produce a third hard-braking event signal corresponding to a third hard-braking event level in response to the first and second signals in the event both the first and second hard-braking event levels are reached during a braking event, the braking event commencing upon the detection of any of the first and second hard-braking event signals and ending upon the end of both of the first and second hard-braking event signals; and

an indicator coupled to the hard-braking event detector and operable to selectively indicate the hard-braking event level that has been detected.

60. An apparatus according to claim 59 in which the hard-braking event detector has an input for receiving lateral acceleration signals indicative of the lateral acceleration of the vehicle, and wherein the hard-braking event detector is operable to block the indication of a hard-braking event level in the event the vehicle lateral acceleration as indicated by the lateral acceleration signal exceeds an acceleration threshold.

61. An apparatus according to claim 60 in which the hard-braking event detector blocks the indication of a hard-braking event level after the end of a hard-braking event which resulted in the determination of the hard-braking event level.

62. A method of advising a vehicle operator of vehicle of driving conditions which create an increased risk of loss of control of the vehicle, the method comprising:

determining the existence of at least one rollover advisory event during which the risk of vehicle rollover is unacceptably high;

advising the vehicle operator of the existence of an unacceptably high rollover risk following the end of the rollover advisory event.

63. A method according to claim 62 comprising the act of selectively advising the vehicle operator of a speed reduction recommendation following the end of the rollover advisory event.

64. A method of advising a vehicle operator of vehicle of driving conditions which create an increased risk of loss of control of the vehicle, the method comprising:

determining the existence of at least one rollover advisory event during which the risk of vehicle rollover is unacceptably high;

advising the vehicle operator of the existence of an unacceptably high rollover risk following the end of the rollover advisory event;

comprising the act of determining the existence of at least one hard-braking event during which the risk of loss of control of the vehicle due to braking is unacceptably high; and

selectively advising the vehicle operator of the existence of the hard-braking event following the end of the hard-braking event.