Patent Document ID: 20020082806
Application ID: 09938616
Patent Flag: 0

Claim One:
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: conflict opportunity&equals;(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 &lcub;(opposition flow rate in the opposition lane)*(exposure time of traffic flow to opposition lane)/(−3600) &rcub;; 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 &lcub;(arrival flow rate in the arrival lane)*(duration time of arrival traffic flow lane)/(−3600)&rcub;; 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; calculating the safety rating for the number of accident, injury and fatality involvements based on specific mathematical formulae; 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.