CE 515x

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CE 515x. Initial Instructions Work in teams of 2 - Get a new team mate (i.e., one who is not your partner for the term project). Submit only one set of files/results for the entire team. Train Acceleration, Deceleration, and Impact on Capacity.

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### CE 515x

Initial Instructions

Work in teams of 2 - Get a new team mate

(i.e., one who is not your partner for the term project).

Submit only one set of files/results for the entire team.

Train Acceleration, Deceleration,

and Impact on Capacity

For a given 10 mile section of track, there is a proposed speed reduction from 50 mph to 30 mph

for a 5 mile stretch. All trains on this track consist of 50 70-ton, 75’ cars pulled by 4 2000 hp, 100’

diesel-electric units. All needed data on the performance of this train configuration are given on

the following graphs taken from Hey (Table 10.1, Figures 10.3, 10.4, 10.9, and 10.10).

Assume 0% grade throughout the area being examined. Recall flow = density times speed! You may wish to utilize equations 10.6 and 10.12 shown below (not strictly necessary). Note that the slow speed section limits capacity.

Figure 1. Visualization of the Problem

t = 95.6 (vf - vi)

L = 70 (vf2 - vi2)

Fa’

Fa’

Equation 10.12: Time of Acceleration

Equation 10.6: Length of Acceleration

Acceleration/Deceleration considerations (cont.)

Part 1

1. Determine the travel time difference between the before case (50 mph everywhere) and the after case (50 - 30 - 50). Assume train slows to 30 mph prior to 30 mph zone and accelerates to 50 mph after reaching other end of the 30 mph zone (i.e., treat the speed limit as if it only applied to the lead locomotive - obviously as it accelerates out of the restricted zone, trailing cars will exceed the speed limit).

2. Determine maximum traffic flow (in trains per hour) with a “block” signaling system. Trains must never occupy the same block. See p. 126 - 135 in Armstrong for definition of block signaling system. Assume blocks are 1/2 mile long, with one signal at each end of the given section and spaced throughout. Trains must be able to come to a complete and safe stop if a train ahead is stopped. Hint: Compute the flow for 30 and 50 mph sections separately.

3. Determine maximum traffic flow (in trains per hour) assuming trains are equipped with GPS systems. Run trains as close together as safety (stopping distance) allows. Again, compute the flow for 30 and 50 mph sections separately.

Part 2

Assume that due to construction, a 1 mile section in the center of the 30 mph zone is reduced to one track, which has to support two-way traffic.

1. Determine maximum traffic flow assuming alternating trains eastbound then westbound.

a. First, determine time through the zone with the trains having to stop upon reaching the construction zone, waiting for opposing traffic to pass and then exiting the area.

b. Second, determine the maximum traffic concentration with trains alternating through the zone without slowing below 30 mph.

Part 3

Consider the effects of a +1% up-grade on the train described. The grade is 2 miles long. Find the speed of a train at the top of the grade if it enters the bottom of the grade at 50 mph. How long does it take the train to get back to 50 mph (time and distance)?