Traffic safety prediction model

• US 5,798,949 A
• Filed: 08/09/1996
• Issued: 08/25/1998
• Est. Priority Date: 01/13/1995
• Status: Expired due to Fees

• Current Assignee: Alan Richard Kaub
• Original Assignee: Alan Richard Kaub
• Inventors: Kaub, Alan Richard
• Primary Examiner(s): Teska, Kevin J.
• Assistant Examiner(s): LOPPNOW, MATTHEW CLAY
• Application Number:
  US08/689,651
• Time in Patent Office: 746 Days
• Field of Search: 364/578, 364/436, 364/437, 364/438, 340/995, 340/905
• US Class Current: 703/6
• 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

The present invention provides an 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. An apparatus 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 the group consisting of stop mode, caution mode, and go mode comprising:

data storage means for storing traffic flow information, opposition flow information, intersection and roadway data, and a conflict to accident ratio;

input means for entering information into said data storage means;

a processor including a first and a second mathematical component for processing said data to yield processed data;

output means for displaying said processed data; and

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

wherein said first mathematic component calculates a total expected number of conflicts between the traffic flow and the opposition flow for each intersection along the roadway; and

wherein said second mathematical component computes an expected number of accidents for each intersection along the roadway by dividing said number of conflicts by said conflict to accident ratio.

2. The apparatus of claim 1, further comprising:

said data storage means further including a table of injury to accident ratios and average intersection speeds; and

said processor including a third mathematical component for determining an average intersection speed from the traffic flow data in said data storage means and selecting one of said injury accident ratios corresponding to said average intersection speed, and multiplying said expected number of accidents for each intersection along the roadway by said injury to accident ratio to determine an expected number of property damage and injury involvements for each intersection along the roadway.

3. The apparatus of claim 2, further comprising:

said data storage means further including an injury to kill ratio;

and said processor including a fourth mathematical component for multiplying said expected number of injury involvements for each intersection along the roadway to determine a number of fatal and non-fatal injury involvements.

4. The apparatus of claim 3, further comprising:

said data storage means further including a conversion table of total non-fatal and fatal injury involvements to Intersection Safety Level of Service ratings; and

said processor includes a fifth mathematical component for entering said number of fatal and non-fatal injury involvements into said conversion table and retrieving a corresponding Intersection Safety Level of Service.

5. The apparatus of claim 4, further comprising:

said processor further including a sixth mathematical component for summing said fatal and non-fatal injury involvements for each of the intersections to produce a roadway total number of fatal and non-fatal injury involvements.

6. The apparatus of claim 5, further comprising:

said data storage means further including roadway conversion tables having a plurality of roadway total number of total injury involvements, a plurality of roadway classifications, and a plurality of roadway safety levels of service; and

said processor including a seventh mathematical component for entering said roadway total number of fatal and non-fatal injury involvements, a roadway classification, and retrieving a corresponding one of said plurality of roadway safety levels of service.

7. The apparatus of claim 6, further comprising:

said processor further including an eighth mathematical component for calculating a minimum safe distance spacing between the intersections.

8. The apparatus of claim 7, said input means further including means for sensing traffic flow.

9. The apparatus of claim 8, said traffic flow sensing means being a photolog.

10. The apparatus of claim 1, further comprising:

said data storage means including a table of injury to accident ratios and average intersection speeds, and further includes a conversion table of total non-fatal and fatal injury involvements to Intersection Safety Level of Service ratings;

said processor including a third mathematical component for determining an average intersection speed from said traffic flow information in said data storage means and selecting one of said injury accident ratios corresponding to said average intersection speed, and multiplying said expected number of accidents for each intersection along the roadway by said injury to accident ratio to determine an expected number injury involvements for each intersection along the roadway;

and said processor including a fourth mathematical component for entering said number of fatal and non-fatal injury involvements into said conversion table and retrieving a corresponding Intersection Safety Level of Service rating.

11. An apparatus 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 the group consisting of stop mode, caution mode and go mode comprising:

input means for entering traffic flow and opposition flow information;

data storage means for storing traffic flow information, opposition flow information, and intersection and roadway data;

a processor to yield processed data;

output means for displaying said processed data; and

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

wherein said first processor calculates an total expected number of accidents between the traffic flow and opposition flow for each intersection along the roadway.

12. 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; and

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.

13. The method of claim 12, 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 object accident model conflicts.

14. The method of claim 13, 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.

15. The method of claim 14, 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.

16. The method of claim 15, 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.

17. The method of claim 16, 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.

18. The method of claim 17, 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.

19. The method of claim 18, 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.

20. The method of claim 18, 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

e (natural logarithmic base) raised to power of {(arrival flow rate in the arrival lane)*(duration time of arrival traffic flow lane)/(-3600)}.

21. The method of claim 18, further comprising the step of calculating the probability of opposition to the arrival in the opposition lane as a negative binomial distribution as

e (natural logarithmic base) raised to power of {(opposition flow rate in the opposition lane)*(exposure time of traffic flow to opposition lane)/(-3600)}.

22. The method of claim 12, 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 an ISLOS chart which includes an ISLOS letter rating for an intersection for total accidents, injury and fatality involvement quantities;

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;

conflict opportunity=(Probability of Opposition from the Opposition flow)* (Probability of Arrival flow)*(Number of arrivals per time period of traffic flow in the traffic flow lane);

calculating a Probability of Opposition from the Opposition flow as a negative binomial distribution as e (natural logarithmic base) raised to power of {(opposition flow rate in the opposition lane)*(exposure time of traffic flow to opposition lane)/(-3600)};

referring to the conflict to accident chart to determine a conflict to accident ratio for the traffic flow through the intersection;

calculating a probability of arrival flow as a negative binomial distribution as e (natural logarithmic base) raised to power of {(arrival flow rate in the arrival lane)*(duration time of arrival traffic flow lane)/(-3600)};

calculating the total number of accidents by dividing the number of conflict opportunities by the conflict to accident ratio;

referring to the injury ratio chart to determine a number of fatalities, injuries, and property damage involvements for the total number of accidents;

referring to the ISLOS chart to determine the ISLOS safety rating for the number of accident, injury and fatality involvements;

determining a number of roadway accidents as a sum of total accidents for each intersection on the roadway;

determining a number of roadway injury and fatality involvements as the sum of injury and fatality involvements for each intersection along the roadway; and

referring to the RSLOS chart to determine an RSLOS safety rating for the number of roadway injury and fatality involvements.