American Audio VELOCITY - REV 4-05 Betriebsanleitung PDF herunterladen (Seite 73)

METRO RAIL DESIGN CRITERIA SECTION 9 / SYSTEMS

DE304.09 9-68 Revision 4 : 05/09/12

Metro Baseline Re-Baseline: 04/29/10

 The maximum block length shall be 2,000 feet.

 All track circuits with a Maximum Authorized speed (MAS) exceeding 35 mph shall

have at least one intermediate speed code before “STOP”.

 Exceptions to the above criteria shall be reviewed on a case-by-case basis.

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.

9.4.4.2 Train Detection

The signaling system shall detect all cars operating independently or in consist, and any

other rail vehicle present, except hi-rail vehicles.

The presence of a rail vehicle in a section of the route shall be detected continuously by

means of track circuits.

Detection of the occupation of the track circuit shall be fail-safe, such that a de-energized

position is interpreted as an occupation of the track circuit.

In the event of a temporary loss of detection, the design shall ensure that indication of the

presence of a rail vehicle in a section will be maintained while a rail vehicle is actually in the

section.

If a rail vehicle is parted in an unscheduled manner, the signal system shall ensure that all

parts of the rail vehicle are detected. The signal system shall ensure that safe separation is

maintained between the parted vehicle and all other rail vehicles.

The minimum effective length of a track circuit shall be longer than the maximum inner

wheelbase of all vehicles used on this track.

For track circuits used to control signals and locking functions, including grade crossing

activation devices, the minimum shunt sensitivity shall be 0.25 Ohms. The shunting

requirements shall be met for ballast conditions of 5 ohms per thousand feet or greater.

9.4.4.3 Broken Rail Detection

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American Audio VELOCITY - REV 4-05 Betriebsanleitung Seite 73