24 May 2015

Going the Extra Inch

Assisted level boarding on
Amtrak's Northeast Corridor
To enable wheelchair users to board a train without assistance, the Americans with Disabilities Act (ADA) requires level boarding platforms to have a maximum 3-inch horizontal gap with the train floor, and a maximum height mismatch of 5/8 inch (see 49 CFR 38.93).  When this specification is met, wheelchair users can safely and quickly board a train by simply rolling across the narrow gap between the platform and the train, giving it no more thought than when using an elevator.

Today, few commuter rail systems in the United States offer this level of accessibility.  The NCTD Sprinter (see video) may be the only one, and is often classified as "light" rail.  U.S. systems with level boarding (such as in the Northeast) have a gap of six inches or more between the platform and the train, requiring the use of bridge plates for a wheelchair user to board.  As shown in the photo above, train crew members must assist with the process of deploying the bridge plate, monitoring the wheelchair, and re-stowing the bridge plate.  Assisted boarding can easily extend station dwell times and cause delays, even on a rail system with level boarding.  These delays are allowed for by padding the time between successive trains, to prevent a delay from cascading to multiple trains.

So, just build the platforms close enough to the tracks and we're done, right?  It's not quite that easy.

Dynamic Vehicle Envelope

Dynamic envelope as defined
for Caltrain electrification
When trains are moving at speed, they can sway from side to side.  Suspension failures or shifting loads could even cause them to sag or lean to one side, requiring additional clearance between the track and nearby obstacles.  Station platforms form one such obstacle.  Caltrain's electrification RFP defines a dynamic vehicle envelope (shown at left, from page 95 of this PDF document) that encompasses the range of motion that can be expected from Caltrain's existing diesel fleet, future high-speed trains, and freight trains that use the peninsula corridor.  The dimensions of the dynamic envelope constrain how far from the track center line any future level boarding platforms would have to be set back, in order to prevent what is known as a "platform strike" from a train passing at speed.
  • 8" platforms (existing) are 64" from track center
  • 25" platforms would have to be 67" from track center
  • 30" platforms would have to be 68" from track center
  • 50" platforms would have to be 70" from track center
Meeting the ADA Gap

Unassisted level boarding in Zurich
(Siemens photo)

The vehicle envelope, because it is dynamic, forces a clearance between platforms and trains that is wider than the 3-inch ADA maximum for unassisted boarding.  To provide unassisted boarding without bridge plates, the gap can be bridged automatically by a moving step that extends from the train, a moment before the door opens.  As shown in the photo at right, this step is the key to ADA-compliant unassisted boarding for wheelchair users, and provides a more comfortable boarding interface for bicycles, strollers, luggage, and anything else with wheels.  The step retracts after the doors close, a moment before the train departs.

These gap-filling steps are quite common outside the confines of U.S. commuter rail, and all major vehicle manufacturers worldwide can provide them if the customer asks.  Video examples:
Another common and useful train feature is an automatically leveling suspension, to control the plus or minus 5/8" vertical alignment between the train floor and the platform regardless of passenger load or wheel wear.  A nice bonus of such a system is that it can measure passenger loads in real time.  This too can be provided by vehicle manufacturers if the customer asks.

Caltrain's Approach: What Gap?

Caltrain is now taking a "not to preclude" approach to level boarding, attempting to future-proof the new EMU fleet for any future decision regarding level boarding, pending the outcome of additional planning for the Caltrain / high-speed rail blended system.  This approach is largely a result of not having seriously thought about or planned for level boarding until quite recently.

[Update 6/14/2015: turns out that Caltrain's EMU RFP does require the ADA gap specs for unassisted level boarding!  My source had it wrong.]
As it turns out, Caltrain has no intention to comply with the ADA gap requirement.  Never mind the gap.  As will be apparent in the upcoming vehicle RFP, the new EMU fleet will comply with the ADA using crew-assisted boarding with bridge plates, even after level boarding platforms are built and regardless of the selected platform height.

If Caltrain fails to specify gap-filling steps and leveling suspensions for their new EMU fleet, then wheelchair users will still need crew assistance to board or alight, resulting in random and unpredictable impacts on station dwell times.  Such a failure would preclude reliable and punctual operation of the blended system, increase the amount of timetable padding between trains, and limit the capacity that can be extracted from the peninsula rail corridor before expensive and controversial infrastructure upgrades become unavoidable.  Gap-filling steps and leveling suspensions are perfect examples of small off-the-shelf features that pay off in the long run.

In order "not to preclude" an efficient blended system that extracts the highest capacity from limited infrastructure, Caltrain should require that the new EMU fleet be equipped for ADA-compliant unassisted wheelchair boarding, once new level boarding platforms become available.  Because the new fleet will be in service until the year 2050, this capability cannot be an afterthought and must be engineered into the new trains from the outset.

17 May 2015

CBOSS Headed for Trouble?

The button we may soon have
to press. Photograph by
Sander van der Vel
Caltrain's new Positive Train Control (PTC) system, known as CBOSS, appears to be running into serious technical difficulties just as the program enters its most challenging phase: testing and commissioning.

The system was originally proposed to be built on top of GE Transportation's Interoperable Incremental Train Control System (I-ITCS) technology, an approach that was touted as advantageous for being "off the shelf."  There are subtle signs that things aren't going so well:
  • This month's CBOSS project status update states rather cryptically that the top challenge for the project is GE software release delays.  These delays could be related to the recent purchase of GE's Transportation arm by the French firm Alstom, which already offers a range of PTC technologies that could make the ITCS product line redundant.
  • The technical requirements for the electrification RFP state (see PDF p. 251 of 2,840) that CBOSS is built on Wabtec's Interoperable Electronic Train Management System (I-ETMS), the main competitor to GE's I-ITCS.  Switching from ITCS to ETMS would be like changing the foundation of a house after the roof is completed.
  • Section 4.13.1 of the electrification RFP document describes the electrification project scope, stating that "The Contractor shall provide the signal, train control and grade crossing systems"... a definition of scope that overlaps significantly with the CBOSS project.
  • Section of the electrification RFP document further describes items that are in the scope of the electrification program, including:
    • System-wide track circuit replacement
    • Manufacturing and assembly of signal enclosures, including installation and wiring
    • Installation of signal enclosures, wayside signals, cables, and cable infrastructure
    • Field testing of the signal system and integrated testing with the electrification, EMU, CBOSS/PTC and other interdependent systems
    • All work associated with the modification of the signal system required for the Project, including the CBOSS/PTC system as necessary and as required by all regulatory agencies, including the FRA, MUTCD and CPUC. The Contractor shall ensure that its wayside CBOSS/PTC systems are 100% compatible with the existing CBOSS/PTC systems that its systems will interface with.
  • The electrification RFP document continues for dozens of pages, describing how an almost entirely new signaling system will have to be installed as part of the electrification project.  What CBOSS was supposed to "overlay" will be largely replaced.
Is there a major architectural change in the CBOSS project that Caltrain staff failed to disclose to the board?  The entire CBOSS budget of $231 million (an astronomical sum for just 50 route-miles of railroad) having already been appropriated and mostly spent, are we about to see large cost overruns get squirreled away in the small print of the electrification RFP?  Is the respective scope of the CBOSS and electrification projects sufficiently well delineated to preclude spending money twice on the same item under two separate contracts?

A faint odor of fish wafts over the whole affair.