For a population with a standard deviation of o-8, how large a sample is necessary to havea standard error that is: Less than or equal to 4 points? bLess than or equal to 2 points? Less than or equal to 1 point?

2.8 A rear-wheel-drive car weighs 2600 lb and has an 84-inch wheelbase, a center of gravity 20 inches above the roadway surface and 30 inches behind the front axle, a drivetrain efficiency of 85%, 14-inch-radius wheels, and an overall gear reduction of 7 to 1. The car's torque/engine speed curve is given by the equation Me=6ne - 0.045n^2c. If the car is on a paved, level roadway surface with a coefficient of adhesion of o.75,determine its maximum acceleration from rest.

3-21What is the distance required to stop an average passenger car when brakes are applied on a 3.3% downgrade if that vehicle was originally traveling at 35 mi/h?

An approach to a pre timed signal has 25 seconds of effective green in a 60-second cycle. The approach volume is500 veh/h and the saturation flow rate is 1400 veh/h. Calculate the average vehicle delay assuming D/D/1 queuing.

2.26 A driver traveling down a 4% grade collides with a roadside object in rainy conditions, and is issued a ticket for driving too fast for conditions. The posted speed limit is 65 mi/h. The accident investigation team determined the following: The vehicle was traveling 40 mi/h when it struck the object, braking skid marks started 205 ft before the struck object, the pavement is in good condition, and the braking efficiency of the vehicle was 93%. Using theoretical stopping distance, assuming aerodynamic resistance is negligible, and with the coefficient rolling resistance approximated as o.015, should the driver appeal the ticket? Why or why not?

12. (15 points) The Alabama crash data show that a stop-controlled intersection in Tuscaloosa has an average of 15 crashes per year. This stop-controlled intersection is causing excessive delays during peak hours. The City plans to convert the intersection into a roundabout which is often associated with a greater operational efficiency than a stop-controlled intersection. Before the conversion, the City wants to know whether the project can also improve the safety. If yes, please calculate the number of crashes that could be reduced by this project.

Problem 3 An engineer wishing to determine whether there is a statistically significant difference between the average speed of passenger cars and that of large trucks on a section of highway, collected the data shown below. Determine whether the engineer can conclude that the average speed of large trucks is the same as that for passenger cars. In other words, is the average speed of the large trucks significantly different than the average speed of the passenger cars? (0.50 pts) You must show your work. (0.50 pts)

3-22A driver on a level two-lane highway observes a truck completely blocking the highway. The driver was able to stop her vehicle only 30 ft from the truck. If the driver was driving at 55 mi/h, how far was she from the truck when she first observed it (assume perception-reaction time is 1.5 seconds)? How far was she from the truck at the moment the brakes were applied (use a/g = 0.35)?

5. (5 points) The figure below shows the horizonal and vertical alignment of a 500-ft road segment. The Point A is at Station 100 + 20.00. The distance along the road segment is noted for every 100-ft. Determine: a. The stations of B, C, D on the segment. b. The distance from A to B on the horizontal alignment. b.Th dištañčê from A tó B on the horizontal alignment.c. The distance from C to D on the vertical alignment.

1.A new sports car has a drag coefficient of 0.30 and a frontal area of 21 ft2, and is traveling at 110 mi/h. How much power is required to overcome aerodynamic drag if ρ = 0.002378 slugs/ft3? A. 84.4 ft-lb/s B. 35.4 ft-lb/s C. 57.2 ft-lb/s D. 161.3 ft-lb/s

06.6) A freeway is being designed for a location in rolling terrain. The expected free-flow speed is 55 mi/h. During the peak hour, it is expected there will be a directional peak-hour volume of2700 vehicles and 18% heavy vehicles. The PHF is expected to be 0.88. If a level of service no worse than D is desired, determine the necessary number of lanes. (20%)