Rail: Interlocking Turnouts

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Interlocking Turnout

Primary Guidance

  • The minimum turnout size is defined by the operating railroad mode and minimum required speed
  • When a turnout size lower than the minimum requirement must be used, considerations must be given to safety, maintenance, and operations and maintenance cost

Discussion

Turnout size is selected per the minimum required operational speed and to meet the desired purpose to divert the train. The requirements for different operating mode are defined as below:

Light Rail

Typical application of turnout sizes should conform to the following:

  • Mainline: No. 10 Minimum
  • Mainline Emergency Crossover: No. 8 Minimum
  • Yard Lead Track: No. 8 Minimum
  • Yard Track: No. 6 Minimum

Metro

Typical application of turnout sizes should conform to the following:

  • Mainline: No. 8 Minimum
  • Mainline Emergency Crossover: No. 8 Minimum
  • Yard Lead Track: No. 8 Minimum
  • Yard Track: No. 6 Minimum

MARCMaryland Area Regional Commuter Service

Typical turnout size application should conform to the latest Operating Railroad (e.g. Amtrak or CSX) requirements. Typical turnout sizes application for MTAMaryland Transit Authority owned portions of track should conform to the latest requirements of the Operating Railroad to which the MTAMaryland Transit Authority portion connects.

When a turnout size less than stated above is to be used due to difficulties in reconfiguring the track alignment to fit the minimum size or difficulties in construction, considerations must be given to the following:

  • Safety: slower operating speeds must be adhered to at the turnout in order to prevent creating unsafe operations for MDOTMaryland Department of Transportation personnel or the traveling public
  • Maintenance: smaller turnouts can result in conditions such as accelerated wearing of the rail and wheels
  • Operations and Maintenance Costs: estimated construction cost savings associated with smaller turnouts must be compared to Operations and Maintenance costs considering future rail wear and vehicle maintenance

See Also