Traffic safety prediction model

• US 6,662,141 B2
• Filed: 08/27/2001
• Issued: 12/09/2003
• Est. Priority Date: 01/13/1995
• Status: Expired due to Fees

• Current Assignee: Alan R. Kaub
• Original Assignee: Alan R. Kaub
• Inventors: Kaub, Alan R.
• Primary Examiner(s): Hoff, Marc S.
• Assistant Examiner(s): O MALLEY, MARY CATHERINE
• Application Number:
  US09/938,616
• Publication Number:
  US 20020082806A1
• Time in Patent Office: 834 Days
• Field of Search: 702/181, 702/33, 702/36, 702/40, 702/142-143, 702/156, 702/159, 702/176-180, 702/182-183, 702/187-188, 340/902-904, 340/907, 340/916, 340/963, 701/117, 701/301
• US Class Current: 702/181
• CPC Class Codes: G08G 1/0104 Measuring and analyzing of parameters relative to traffic conditions
• CPC Class Codes: G08G 1/164 Centralised systems, e.g. external to vehicles

Abstract

A Traffic Safety prediction Computer Program (TRAF-SAFE) and sub-models for predicting the number of accidents, injuries and fatalities expected annually at an intersection or series of intersections based on the particular intersection and roadway features. A finite analysis approach to an intersection is used to break the intersection into discrete elements such as lanes, turnbays, stop control signals, and traffic flow rates. The total annual expected accidents can then be calculated as a summation of the interrelation of the individual elements. A Poisson'"'"'s distribution is used to statistically estimate the likelihood of the individual vehicles occurring within a discrete time frame being investigated. The conflict probabilities between various permutations of the traffic flow is then calculated and summed to determine the number of conflicts for the intersection or roadway. The conflicts are then converted to expected accidents, and the accident level is converted to injury involvements and Safety Levels of Service for the intersection and roadway.

Claims

1. A method for determining a level of safety for a roadway having a traffic flow and an opposition flow and at least one intersection, wherein each intersection includes a plurality of approaches, each approach having at least one lane, each lane having at least one traffic control device, and each traffic control device having at least one mode chosen from a stop mode, caution mode, and go mode, comprising the steps of:

providing a processor, input means, output means, and data storage means;

providing a data bus connecting the input means, the output means, the data storage means, and the processor;

providing a conflict to accident chart which includes a conflict to accident factor for traffic flow rates through the intersection;

determining a number of conflict opportunities for each of four accident models, wherein the four accident models include angle collision, rear-end collision, side-swipe collision, and fixed object collision models;

providing means for sensing traffic flow chosen from the group consisting of photologs, photosensors, pressure cables, and tabulators;

providing a critical gap chart which includes the exposure time for a vehicle for given intersection dimension data;

providing an injury ratio chart which includes a number of fatalities, injuries, and property damage involvements per number of accidents;

providing a RSLOS chart which includes a RSLOS letter rating for a roadway for total injury and fatality involvement quantities for each of four classes of roadway;

calculating each of the four accident models as a sum of conflict opportunities occurring during the stop modes, caution modes, and go modes of the traffic control devices;

calculating a number of conflicts during the stop modes, caution modes, and go modes for traffic control devices, as a sum of conflict opportunities occurring for traffic flow in each lane of each approach;

calculating a number of conflict opportunities occurring for traffic flow in each lane of each approach as a sum of conflict opportunities caused by opposition flow in each lane of each approach, wherein a conflict opportunity for one lane of traffic flow versus one lane of opposition flow is calculated as follows;

2. A method for determining a level of safety for a roadway having a traffic flow and an opposition flow and at least one intersection, wherein each intersection includes a plurality of approaches, each approach having at least one lane, each lane having at least one traffic control device, and each traffic control device having at least one mode chosen from a stop mode, caution mode, and go mode, comprising the steps of:

providing a processor, input means, output means, and data storage means;

providing a data bus connecting the input means, the output means, the data storage means, and the processor;

providing a conflict to accident chart which includes a conflict to accident factor for traffic flow rates through the intersection;

determining a number of conflict opportunities for each of four accident models, wherein the four accident models include angle collision, rear-end collision, side-swipe collision, and fixed object collision models; and

calculating the safety rating for the number of accident, injury and fatality involvements based on specific mathematical formulae using real-time, dynamic parameter adjustments.

3. The method of claim 2, further comprising the steps of:

providing means for sensing traffic flow chosen from the group consisting of photologs, photosensors, pressure cables, and tabulators;

providing a critical gap chart which includes the exposure time for a vehicle for given intersection dimension data;

providing an injury ratio chart which includes a number of fatalities, injuries, and property damage involvements per number of accidents;

providing a RSLOS chart which includes a RSLOS letter rating for a roadway for total injury and fatality involvement quantities for each of four classes of roadway;

calculating each of the four accident models as a sum of conflict opportunities occurring during the stop modes, caution modes, and go modes of the traffic control devices;

calculating a number of conflicts during the stop modes, caution modes, and go modes for traffic control devices, as a sum of conflict opportunities occurring for traffic flow in each lane of each approach;

calculating a number of conflict opportunities occurring for traffic flow in each lane of each approach as a sum of conflict opportunities caused by opposition flow in each lane of each approach, wherein a conflict opportunity for one lane of traffic flow versus one lane of opposition flow is calculated as follows;

4. The method of claim 2, further comprising the steps of:

calculating the mean number of person trips made in a vehicle in a lifetime given as an estimated length of a lifetime*365 days per year*a ratio of the average number of vehicle trips per household in a given community, state, region or nationally divided by the average number of persons per household in a given community, state region or nationally;

calculating the probability that a person will die in any one vehicle trip over their lifetime as the summation of the [{probability of a fatal crash in a single trip over a lifetime of travel as given by the negative binomial distribution as e (natural logarithmic base) raised to a power of the lifetime risk of death in a vehicle crash out of 1000 lifetimes}minus 1.0] divided by the mean number of person trips made in a vehicle in a lifetime;

calculating the probability of injury in one trip over a lifetime as given by the probability that a person will die in any one vehicle trip over their lifetime, multiplied by a ratio of total number of annual injury crashes (nationally or locally) per year divided by the total number of annual fatal crashes per year (nationally or locally);

calculating the maximum allowable number of annual injury crashes allowable for an intersection to remain classified as “

Safe”

as given by a ratio of vehicle injuries occurring at this specific type of traffic control (stop or signal control, nationally or locally) over all intersections (nationally or locally) to the sum total of all vehicle injuries occurring (nationally or locally) regardless of traffic control type*the total number of person trips entering the intersection throughout the year*{1.0 minus a negative binomial distribution as e (natural logarithmic base) raised to a power of {(−

mean number of person trips made in a vehicle in a single year)*(the probability of injury in one trip over a lifetime)};

calculating Intersection Safety Levels of Service (ISLOS) with ranges of A-F with each range defined as a 1/5 ratio of the maximum number of annual injury crashes allowable for an intersection to remain classified as “

Safe”

;

defining a “

safe”

intersection for planning purposes as one where the Safety Level of Service is in ISLOS levels of “

A, B, C or D”

;

defining a “

safe”

intersection for operations (current year) purposes as one where the Safety Level of Service is in ISLOS levels of “

A, B, C, D or E”

; and

defining an “

unsafe, hazardous or dangerous”

intersection for planning or operations purposes as one where the Safety Level of Service is in ISLOS level “

F”

.

5. The method of claim 2, further comprising the step of calculating the total expected number of conflicts as a sum of four accident model conflicts, selected from the group consisting of angle accident, rear-end accident, side-swipe accident, and fixed-object accident model conflicts.

6. The method of claim 5, further comprising the step of calculating at least one of the four accident model conflicts as a sum of conflicts calculated for each of the traffic control modes.

7. The method of claim 6, further comprising the step of calculating a number of conflicts expected during at least one mode of the traffic control device as a sum of conflicts expected for each lane of each approach.

8. The method of claim 7, further comprising the step of calculating a number of conflicts expected for at least one lane of one approach as a sum of conflicts caused by opposition flow in each opposition lane of each opposition approach.

9. The method of claim 8, further comprising the step of calculating the conflicts caused by the opposition flow of each opposition lane of each opposition approach as a product of the number of arrivals per time period of traffic flow in the traffic flow lane and the probability of conflict between the arrival and opposition flows during the time period that the arrival flow is exposed to conflict from the opposing flow.

10. The method of claim 9, further comprising the step of calculating the probability of conflict between the arrival and opposition flows from the opposition lane as the product of the probability of an arrival of a vehicle in at least one lane of one approach during a time period defined by the duration of the arrival time, and the probability of opposition to the arrival in the opposition lane from at least one lane of one approach during the time period which the arrival vehicle requires to complete the arrival maneuver.

11. The method of claim 10, further comprising the step of calculating the probability of arrival of a vehicle in at least one lane of one approach as a negative binomial distribution.

12. The method of claim 10, further comprising the step of calculating the probability of arrival of a vehicle in at least one lane of one approach as a negative binomial distribution as

13. The method of claim 10, further comprising the step of calculating the probability of opposition to the arrival in the opposition lane as a negative binomial distribution as