American Audio VELOCITY - REV 4-05 Betriebsanleitung PDF herunterladen (Seite 48)

METRO RAIL DESIGN CRITERIA SECTION 9 / SYSTEMS

DE304.09 9-43 Revision 4 : 05/09/12

Metro Baseline Re-Baseline: 04/29/10

The cab signal system shall impose speed restrictions on the approach to stations with an

at-grade crossing on the exit side of the station. In the normal direction of traffic the

following design requirements shall be followed:

 Speed code reduction, or removal of cab code shall occur on the approach to, or the

exit from, the station to ensure that a train that fails to make a station stop, or does

not make a full 20-second dwell, cannot enter the crossing unless the entrance

gates are fully down.

 Speed code reduction, or removal of cab code shall, never–the-less, maximize the

train speed into the station.

 Speed code reductions shall be calculated using the Civil Braking Distance formula.

 Speed code reductions shall occur at a point no further than 120% of the Civil

Braking Distance from the near side of the crossing.

 Crossings shall be activated automatically, assuming a 20-second station dwell.

Once the entrance gates are down, full speed cab code shall be available.

 Where the crossing is within 100 feet of the station, a TWC system shall be provided

to enable crossing calls to be called or cancelled.

9.4.2.2 Safe Braking Distance Model

9.4.2.2.1 Introduction

The Safe Braking Distance (SBD) is the calculated distance that a worst-case train will

travel between the time that a speed reduction is commanded until the required speed

reduction is achieved. The train operator is in control of the speed with the cab signal

system providing over-speed protection only. The design shall utilize the SBD formula for all

safety braking requirements.

The Civil Braking Distance (CBD) is the calculated distance that a train will travel between

the time that a civil speed reduction is commanded until the required speed reduction is

achieved. The train operator is in control of the speed with the cab signal system providing

over-speed protection only. The CBD formula shall not be applied to safe train separation.

9.4.2.2.2 Initial Entry Speed

For SBD and CBD calculations, an initial entry speed (S) is used, which is derived from a

combination of Cab Signal Speed (CSS), Cab Signal Tolerance (CST), Cab Signal

Overspeed Allowance (CSO), and the Acceleration Allowance (AA) as follows:

CSS = 55, 45, 35, 25, 20, 10, or 0 mph according to the cab signal code immediately prior

to entry.

CST = Tolerance in speed detection, which shall be as follows:

CSS 55 45 35 25 15 10 0

CST

+0,

-1.5

+0,

-1.5

+0,

-1

+0,

-1

+0,

-1

+0,

-1

+1,

-1

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American Audio VELOCITY - REV 4-05 Betriebsanleitung Seite 48

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