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Location: Texas Department of Transportation (TxDOT) North Central Texas Division Headquarters

Location: Texas Department of Transportation (TxDOT) North Central Texas Division Headquarters. Situation: New Project Brainstorming Review. Current Issues: Significant growth east of Lake Lavon, Growing accident volume through Wylie corridor,

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Location: Texas Department of Transportation (TxDOT) North Central Texas Division Headquarters

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  1. Location: Texas Department of Transportation (TxDOT) North Central Texas Division Headquarters Situation: New Project Brainstorming Review

  2. Current Issues: • Significant growth east of Lake Lavon, • Growing accident volume through Wylie corridor, • Skyrocketing accident repair costs. What do we do?

  3. Brainstorming Suggestions from the team: • Reduce posted Speed Limits, • Push for insurance reform, • Change traffic light schemes to better manage traffic flow, • Expand roads in Wylie corridor, • Staff more patrol cars in Wylie corridor, • Build bridge across Lake Lavon, • Launch campaign encouraging greater public transportation use and carpooling. • Raise taxes on property east of Lake Lavon.

  4. You are assigned to build the case for the following ‘Brainstorming Suggestion’... • Build bridge across Lake Lavon, Lots of questions to address: How do you justify the cost? What is the traffic load? How long will the bridge be? Where are we going for lunch?

  5. Good news. The research department has a few stats that you can use: • 4 lane bridge construction is $1.6M per mile, • TxDOT cost for each injury accident averages $10,000. • Regarding the intersection of FM1378 (Country Club Rd.) and FM2514 (Parker Rd.): • Currently 400,000 vehicles eastbound monthly, • 0.01% are involved in injury accidents in the Wylie corridor, • 70% of eastbound vehicles are destined for Copeville and beyond,

  6. So, how long will this bridge need to be? Let’s take it from the intersection of FM1378 and FM2514 to State Highway 78 and CR549 in Copeville...

  7. Wow, with so much lake, we can’t really walk out the length. How can we measure the distance? Oh, Pythagorean called about lunch? Tell him we are really tied up today…

  8. Here is what we can measure… 3

  9. Here is what we can measure… 3 7

  10. Here is what we can measure… 4 3 7

  11. Here is what we can measure… 4 3 7

  12. So, it appears that we can use some right triangles to determine distances… Someone needs to work on the accident counts and costs that will be avoided by building this bridge…

  13. Of the 400,000 eastbound vehicles, 70% will use the bridge. Of those 70%, 0.01% were in accidents each month, costing $10,000 per accident. Eastbound vehicles that would move to the bridge 400,000 X 70% = 280,000 Injury accidents per month (avoided) 280,000 X 0.01% = 28 Monthly accident costs (eliminated) 28 X $10,000 = $280,000 Annual accident costs (eliminated) $280,000 X 12 months = $3.36M

  14. Again, here is what we can measure… …Now, just a bit of math magic… 4 3 7

  15. Let’s use the point slope formula to determine where on the East-West line we find the hypotenuses of the two right triangles to be perpendicular. This would be where the change of ‘Y’ over the change of ‘X’ for each hypotenuse yields line slopes (m) that are negative reciprocals of one another. m = (y1-y2)/(x1-x2) FM1378-FM2514 intersection is point (0,3) Copeville is point (7,4) Guess is point (3,0) m(FM1378-FM2514) = (3-0/0-3) = -1 m(Copeville = (4-0)/7-3) = 1 Line slopes with common point (3,0) are negative reciprocals.

  16. Here’s that view… 4 3 3 4 7

  17. Now we invite in our friend Pythagorean for application of his theorem… a2 + b2 = c2 where ‘c’ is the hypotenuse of a right triangle. c2 = 32 + 32 = 9 + 9 = 18 c2 = 42 +42 = 16 + 16 = 32

  18. Pythagorean Application #1… 32 4 18 3 3 4 7

  19. Now we can apply Pythagorean’s Theorem again… 32 4 18 3 3 4 7

  20. c2 = a2 + b2 = 18 + 32 = 50 c = square root of 50 = 7.1 Bridge Distance… 7.1 Miles!

  21. The Solution… 7.1 32 4 18 3 3 4 7

  22. Project Summary Bridge construction: 7.1 miles at $1.6M/mile - $11.4M Injury accident cost savings: $280,000 per month Return on Investment (RoI): $11.4M / $280,000 = 41 months

  23. What are other variables that you may need to address? • Projecting future traffic volumes, • Account for some accident cost on new route, • Benefits to other eastbound routes, • Benefit of reduced accident impact to others, • Wildlife sanctuary impacts of bridge, • Planned development in the area. • Westbound relationship to eastbound.

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