1.Fault Tree and Threshold Change Analysis.

In Templeton, MA, the (fictional) intersection of Royalston Road with Route 2 has presented a safety problem to the town; 6,000 cars use the Royalston Road-Route 2 intersection each year and there have been several accidents there over the past decade, some of which proved fatal. Each accident costs the town an average of $150,000 in road repairs, insurance claims, police details, ambulance and EMT costs, and lawsuits. The town of Templeton has contracted you to make some safety recommendations because of your expertise in this area. Your staff has already developed a Fault Tree for this situation, which is presented below. (You will recognize this fault tree as the same one discussed during the Module 6 lecture.) You may safely assume that the fault tree and all its data are correct and complete. Please use a 10-year planning horizon for this exercise.

Probability Scale Quantification of Fault Trees 1 in 10 Frequent 1 in 100 Probable TOP CRASH AT CRASH Probability = 0.001 or 1 in 1000 EVENT MAIN ROAD 1 in 1000 Occasional JUNCTION If 6000 cars use the side road every year, then it is expected that 6-7 crashes per year 1 in 10000 Remote may occur 1 in 100000 Improbable AND 1 in 1 m Extremely Remote CAR AT MAIN SIDE ROAD ROAD CAR FAILS TO JUNCTION STOP P=0.01 OR P=0.131 SIDE ROAD SIDE ROAD CAR CAR DRIVER DRIVER COULD DID NOT STOP NOT STOP P=0.12 OR P=0.011 OR DRIVING DRIVER VISION ROAD TOO BRAKE TYRES TOO FAST TOO ILL OBSCURED SLIPPERY FAILURE WORN P=0.1 P=0.01 P=0.01 P=0.01 P=0.001 P=0.0001 -Option Build an Overpass Install a stoplight and grading Cost $10 million $150,000 Risk Impacted Impac't'It Car at Main Road Reduces the probability of "Car Junction at Main Road Junction" from 0.01 to 0 Car at Main Road Reduces the probability of "Car Junction at Main Road Junction" from 0.01 to 0.003 Reduces probability of "Driving Install Speed Bumps $20,000 Driving too fast too fast" from 0.1 to 0.03 Install Radar Speed $10,000 Driving too fast Reduces probability of "Driving Display too fast" from 0.1 to 0.06 Install additional $2,000 Driving too fast Reduces probability of "Driving Speed Limit signs too fast" from 0.1 to 0.08