SEPI, Inc is an Engineering company started by Sepi Said in 2001 in Wake County. In this activity, you will determine how a stretch of highway in Wake County functions now and how it will function in the future. Initial thought questions: 1. Have you ever been stuck in traffic? 2. List two or three reasons that traffic occurs. 3. List two or three ways to alleviate traffic issues. 4. Describe when roads are functioning at optimal level or traffic conditions are ideal. Scenario: As more people are moving to Wake County, our roads are becoming busier and are no longer functioning at an optimal level. Today, you are a civil engineer at SEPI, Inc. Your job is to analyze the traffic on a 1.25 mile stretch of I-40 in Wake County. This stretch of I-40W is a 4-lane highway (2 lanes in each direction) and has 3 interchanges (exit ramps) in each direction per 6 miles. A survey of the highway has found that the lanes are 12 feet wide with a 4 foot left shoulder, 10 foot right shoulder, and a 2.5% grade. We are going to analyze just the traffic flow traveling eastbound on 1-40. The Traffic traveling eastbound during the morning peak (DDHV) is found to be 2,400 vehicles per hour. The peak hour factor is 0.9. Trucks are 6% of the peak hour traffic. Vocabulary: Free Flow Speed (FFS): the speed drivers drive on a segment of roadway when they feel free to travel at their desired speed and their speed is not impacted by the presence of other vehicles. This would be a low traffic situation. Base Free Flow Speed (BFFS): measured during a time of day with relatively low volume. In practice, most times, Base Free Flow Speed is determined by either the roadway design speed, or by adding 5 mph to the speed limit if it is over 50 mph or adding 7 mph if the speed limit is under 50 mph. Lane Width Adjustment (foy): The effect lane widths have on free flow speed. The narrower a lane, the more the free flow speed is reduced. Right-Side Lateral Clearance (fric): The effect that right shoulder width and the number of lanes in one direction has on free flow speed. Formulas: Free Flow Speed: FFS = BFFS - fly - fRug - 3.22(TRD)0.84 Capacity: c (basic freeway segment) = 2,200+10(FFS - 50) V Demand Flow Rate: up = ; PHF-N.fHV , where:V = DDHV, demand volume under prevailing conditions, (vehicles/hr) PHF = peak hour factor N = number of lanes in analysis direction Heavy Vehicle Adjustment Factor: JHv = 1+PT(BT-1)' where: PT = proportion of trucks in the traffic ET = passenger car equivalent for trucks Density: D = -2, where: S = mean speed of traffic stream under base conditions (FFS) Task 1: Determine the level of service for this stretch of roadway 1. Using the definition above, and the fact that the speed limit on the stretch of 1-40 in question is 55 mph, what is the Base Free Flow Speed? 2. The table below shows the lane width adjustment (mi/h) given the average lane width. Average Lane Width Reduction in FFS, Exhibit 12-20: (ALW) (mi/hr) ALW 212 0.0 Adjustment to FFS for Average Lane Width for Basic 11 S ALW 25% 0.125 2.62 2.37 2.30 2.24 2.17 2.12 2.04 1.99 1.97 0.375 2.62 2.37 2.30 2.24 2.17 2. 12 2.04 1.99 1.97 0.625 2.62 2.37 2.30 2.24 2.17 2.12 2.04 1.99 1.97 -2 0.875 2.62 2.37 2.30 2.24 2.17 2. 12 2.04 1.99 1.97 1.25 2.62 2.37 2.30 2.24 2.17 2.12 2.04 1.99 1.97 1.5 2.6 2.37 2.30 2.24 2.17 2.12 2.04 1.99 1.97 0 0.125 2.62 2.37 2.30 2.24 2.17 2.12 2.04 1.99 1.97Exhibit 12-28: PCEs for a mix of 30% SUTs and 70% TTs % Length Percentage of Trucks (%%) Grade (mi) 2%% 4% 5% 6% 10% 15% 20% >25% 0.375 2.62 2.37 2.30 2.24 2.17 2.12 2.04 1.09 1.07 0.625 2.62 2.37 2.30 2.24 2.17 2.12 2.04 1.09 1.97 0.875 2.62 2.37 2.30 2.24 2.17 2.12 2.04 1.09 1.97 1.25 2.62 2.37 2.30 2.24 2.17 2.12 2.04 1.09 1.97 1.5 2.62 2.37 2.30 2.24 2.17 2.12 2.04 1.09 1.97 0.125 2.62 2.37 2.30 2.24 2.17 2.12 2.04 1.09 1.97 0.375 3.76 2.96 2.78 2.65 2.48 2.38 2.22 2.14 2.08 0.625 4.47 3.33 3.08 2.01 2.6 2.54 2.34 2.23 2.17 0.875 4.8 3.5 3.22 3.03 2.77 2.61 2.38 2.28 2.2 1.25 5.00 3.60 3.30 3.09 2.83 2.68 2.42 2.30 2.23 1.5 5.04 3.62 3.32 3.11 2.84 2.67 2.43 2.31 2.2: 0_125 2.62 2.37 2.30 2.24 2.17 2.12 2.04 1.09 1.07 0.375 4.11 3.14 2.03 2.78 2.58 2.46 2.28 2.19 2.13 0_625 5.04 3.62 3.32 3.11 2.84 2.67 2.43 2.31 2.5 2.23 0_875 5.48 3.85 3.51 3.27 2.06 2.77 2.50 2.36 2.28 1.25 5.73 3.08 3.61 3.36 3.03 2.83 2.54 2.40 2.31 1.5 5.80 4.02 3.64 3.38 3.05 2.8 2.55 2.41 2.32 0_125 2.62 2.37 2.30 2.24 2.17 2.12 2.04 1.09 1.07 3.5 0.375 4.88 3.54 3.25 3.05 2.80 2.63 2.41 2.29 2.22 0_625 6.34 4.3 3.87 3.58 3.20 2.87 2.64 2.48 2.31Exhibit 12-26: PCEs for a mix of 30% SUTs and 70% TTs Percentage of Trucks (%) Length Grade (mi] 2% 49% 5%% 6% 8% 10% 15% 20% 25% 0.875 7.03 1.68 4.16 3.83 3.30 3.12 2.76 2.57 2.46 1.25 7.44 4.87 4.33 3.97 3.50 3.22 2.82 2.62 2.50 0.125 2.62 2.37 2.30 2.24 2.17 2.12 2.04 1.09 1.97 0.375 5.80 4.02 3.64 3.38 3.05 2.84 2.55 2.41 2.32 4.5 0.625 7.90 5.11 4.53 4.14 3.63 3.32 2.90 2.68 2.55 0_875 8.01 5.64 4.06 4.50 3.02 3.56 3.07 2.82 2.67 9.19 5.78 5.08 4.60 3.09 3.62 3.11 2.85 2.70 0.125 2.62 2.37 2.30 2.24 2.17 2.12 2.04 1.09 1.87 0.375 6.8 4.58 4.10 3.77 3.35 3.08 2.73 2.55 2.44 5.5 0.625 9.7 6.09 5.3: 4.82 1.16 3.76 3.21 2.93 2.27 0.875 11.20 8.83 5.9 5.33 1.56 4.09 3.45 3.12 2.03 11.80 7.04 6.11 5.47 4.67 .18 3.51 3.17 2.87 0.125 2 62 2.37 2.30 2.24 2.17 2.12 2.04 1.09 1.97 0.375 7.48 4.90 1.36 3.00 3.52 3.23 2.83 2.63 2.51 6 0.625 10.87 6.66 5.79 5.21 4.46 4.01 3.30 3.08 2.80 0.875 12.54 7.54 6.51 5.81 4.04 4.40 3.67 3.30 3.08 13.02 7.78 6.71 5.98 5.07 4.51 3.75 3.37 3.14 8. What are the units for Density? 9. Determine the Density of this stretch of highway.10. Determine the Level of Service for our stretch of highway. Explain what that means in complete sentences. Level of Service Density (pc/mi/in) Exhibit 12-15 LOS Criteria for Basic A $ 11 Freeway and Multilane Highway Segments B > 11 - 18 C > 18 -26 D > 26 - 35 E > 35 - 45 F Demand exceeds capacity or density > 45Task 2: Traffic Growth and Future Improvement Eastbound morning traffic is expected to grow in this area at 4% per year. Using the information from task 1, determine the number of lanes needed to improve the level of service to the next level in 10 years. 11.The future growth equation, En, = 1 + P)\" where V = 2,400 vehiclesrhour P = 4% as a decimal, and N = 10 years Using this information, the future growth equation is V,, = 2400(1 + .04)\". What will the Volume be in 10 years? 12. If no improvements are made, what is the level of service for this volume in 10 years? 13. How many lanes will be needed to improve the level of service to the next level? For example, if you are at a level of service of B, your goal would be to get to a level of service of A. 14. How many lanes will be needed to improve the level of service to level A based on this growth