American Audio VELOCITY - REV 4-05 Betriebsanleitung PDF herunterladen (Seite 82)

METRO RAIL DESIGN CRITERIA SECTION 9 / SYSTEMS

DE304.09 9-77 Revision 4 : 05/09/12

Metro Baseline Re-Baseline: 04/29/10

9.4.5.2 Safe Braking Distance Model

9.4.5.2.1 Introduction

A. SBD is the calculated distance that a worst-case train will travel between the time

that a speed reduction is commanded at a block boundary and the speed reduction

is achieved. See Contract Drawings for graphic representation. The SBD is the

sum of the following distances:

1. Signal Recognition Distance - The distance traveled from the block boundary to

the point at which the ATP vehicle equipment recognizes the more restrictive

speed limit signal. Calculate the signal recognition distance on the basis of

constant train speed for a maximum time period of 2 sec. Use the maximum

train speed permitted by the overspeed tolerance for the ATP speed limit in

effect just prior to the reception of the changed speed limit signal. See Table 3

for overspeed tolerance.

2. Overspeed Detection Distance - The distance traveled from the point at which

the ATP vehicle equipment recognizes the change of the ATP speed limit to the

point at which the ATP vehicle equipment commands traction power removal

and a service brake application. The train achieves instantaneous maximum

available acceleration per Table 1, with consideration for the effects of track

geometry during this time interval. The worst-case overspeed detection time is

0.75 sec.

3. Brake Assurance Reaction Distance - The distance traveled from the point at

which the ATP vehicle equipment commands a service brake application to the

point at which the ATP vehicle equipment determines that the minimum safe

deceleration rate has not been achieved and commands an emergency brake

application. This time interval is 3.0 sec. maximum. This is inclusive of the

traction power removal time which starts when overspeed is detected and

continues until traction power is removed. The train removes traction power at a

worse-case minimum jerk-limited rate of 1.8 mi/hr/sec². Once tractive effort is

reduced to zero, it remains at zero for the remainder of the interval. Base the

initial acceleration on the available tractive effort per Table 1. The track

geometry shall affect the acceleration throughout this period. For calculation

purposes, the train resistance shall affect the acceleration when the tractive

effort equals zero.

4. Emergency Brake Reaction Distance - The distance traveled from the point at

which the ATP vehicle equipment commands an emergency brake application to

the point at which emergency braking begins to build. Assume tractive effort is

zero for the entire time interval, and base acceleration solely on the effects of

train resistance and track geometry. This time interval is 0.4 sec.

5. Emergency Brake Build-up Distance - The distance traveled from the point at

which emergency braking begins to build to the point at which emergency

brakes are fully applied. The braking rate increases linearly from zero to 1.7

mi/hr/sec in 1.1 sec. Adjust deceleration for track geometry.

6. Emergency Braking Distance - The distance traveled from the point at which the

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