Level Boarding Soon, Fast, and Cheap

Caltrain is working on their level boarding roadmap. If their recent work on grade separations is anything to go by, the capture of the agency by the layers of consultants belonging to the transit industrial complex is likely to result in a gold-plated mega-project approach to delivering level boarding in the late 2030s, where each station platform must be reconstructed from the ground up using cast-in-place methods at a system-wide cost easily topping $2 billion.

We don’t need to let them turn level boarding into another costly and delayed mega-project. Existing platforms need to be raised by just 14” and are perfectly suitable as foundation slabs with built-in drainage, electric, plumbing, grounding and bonding. It can all be done without pouring a single cubic yard of concrete. Better yet: stations don't ever need to be closed during construction!

Note: in this article, we will not revisit the urgent need for level boarding, its advantages for reducing trip times and attracting ridership, improving punctuality, increasing crew/vehicle productivity (not just accessibility), or the choice of 48” versus 22” above top of rail (ATOR). These topics are covered extensively in the archives, accessible by search or by keyword label.

Here’s how to get level boarding done soon, quickly and affordably in five steps.

Step 1: EMU Step Retrofit

Diagram (to scale) of new dual step
arrangement. Fixed step in green.
Retractable gap filler in red, shown
in extended position at 22" platform.

The retractable step modules currently installed on the EMUs are removed and replaced fleet-wide with a new dual step arrangement.

• A fixed (not retractable) step is fitted at 15” ATOR, similar to the step arrangement of the old Bombardier cars, proving the acceptable safety of this configuration. The step is sized to fit inside the allowable vehicle loading gauge. It protrudes outside the tapered profile of the lower car body, with structural fusing built in so that expensive damage to the aluminum primary structure is avoided in case the step is struck e.g. in a grade crossing collision.
• A retractable gap filler step at 22” ATOR that extends flush with EMU lower floor level, overhanging the fixed step. This arrangement exists on Swiss Stadler KISS models, and on MUNI Metro. This mechanism is fitted with ultrasonic sensors that inhibit its deployment at 8” low platforms, on an independent per-car basis, i.e. both doors on each car must sense the presence or absence of a 22” platform face and deploy accordingly. Deployment is controlled by onboard software with no intervention by the train crew.

This dual step arrangement allows an EMU to safely dock at an evolving mix of 22” or 8” platforms, or even at a partially raised (partly 8”, partly 22”) platform in mid construction. As the first step towards level boarding, this upgrade needs to be undertaken immediately in concert with Stadler Rail and their step supplier Bode.

Step 2: Platform Furnishing Modifications

In preparation for raising the level of a platform by 14”, all platform furnishings must be modified for the future height. This preparatory construction is performed without closing stations, although portions of a platform may be temporarily inaccessible as the work is performed during nights and weekends. Work can proceed asynchronously at different stations.

Furnishings fall into three categories:

1. Items that have more than 14” of vertical clearance margin can remain as-is, such as taller shelter canopies, visual messaging signs, light poles, and catenary poles.
2. Items that can be raised straightaway by 14” without affecting their compatibility with an 8” platform are modified, such as perimeter fencing, barriers and railing, Clipper terminals, signage, ticket vending machines, utility cabinets, or modular shelters.
3. Items that can’t be raised until the rest of the platform is also raised, such as benches or garbage cans, are prepared. For benches, 14” leg extension brackets can be prefabricated so the raising can be accomplished quickly.

Concurrently with modifications to existing platform furnishings, new railing or fencing and 14” tall edging is added as needed to the outer perimeter of the platform not facing the tracks.

Step 3: Platform Edge Modules

Concept for a platform edge module

The platform edge modules are  engineered prefabricated assemblies, each 6 to 8 feet long. Caltrain will need many (about 6000 system-wide,) so the non-recurring cost of engineering a good design will be well-amortized over the mass production run. The edge modules have several important design features:

• Lightweight reinforced construction with lifting features to allow handling by pallet jack, small forklift or telescopic handler.
• Mounting holes that allow pinning to the existing concrete platform slab, preventing lateral movement from earthquakes or out-of-clearance trains.
• Integrated 24" wide tactile warning strips and high visibility markings from the factory, eliminating the cost of installing such in the field.
• Jacking pads for precise vertical leveling and horizontal lining of the platform edge, providing the required adjustment to comply with tight ADA clearance tolerances as the track settles or wears, or when track is periodically tamped and lined.
• Resilient rubber platform edges with vertical ribbing that supports the weight of boarding and alighting passengers while also providing longitudinal compliance in case of accidental contact. With an edge offset 68" from track center, ribs another 9" deep would keep hard structures outside the clearance envelope mandated by CPUC General Order 26-D, possibly facilitating a waiver. This also provides a compliant surface with which the train's extended gap filler steps can safely make physical contact for a zero-gap platform interface.
• On the side facing away from the tracks, a step with 7” rise and 12” tread depth, to enable temporary use of the module as a 22” platform prior to the remaining surface of the platform being also raised. This step effectively replaces the train’s step at 15", enabling the station to stay open during construction. Even a partial installation of platform edge modules, if not all are installed within one construction shift, can be operated through: the train will deploy the 22” gap filler where modules are detected, and keep them retracted where portions of the 8” platform remain.

While these edge modules aren't off-the-shelf items, their factory mass production can be made more affordable and field installation quicker than the traditional cast-in-place concrete method familiar to Caltain, especially for a systemwide project involving so many platforms at once. They wouldn't be the first customer for a project like this, with established vendors like Creative Composites Group (USA), A.C. Miller (USA),  HERING Group (Germany), Dura Composites (UK), Poundfield Precast (UK), and doubtless many more.

Step 4: Platform Raising

Cross section (roughly to scale)
of materials used in raising
platforms from 8" to 22"

To bring the remaining platform surface up to 22”, five layers are constructed over the original 8" concrete platform slab that henceforth serves as a foundation, in order from bottom to top:

1. Thin layer of gravel to preserve drainage along the surface of the original platform slab, reusing all existing drainage features.
2. 10” layer of lightweight geofoam blocks with vertical drainage holes. This keeps down the dead load of the raised platform (~40 psf total, most likely well within the structural capacity of elevated stations.)
3. Separator layer made of permeable geotextile, to prevent fouling of the underlying layers.
4. Thin layer of compacted sand.
5. Platform topping layer of 3” thick interlocking concrete pavers, similar to German practice.

The finished layers of the raised platform can straightforwardly be reworked or modified as needed (for example, relocating platform furnishings) without resorting to concrete demolition.

Where electrical junction boxes, pull boxes or water valve boxes are embedded in the existing 8” platform surface, a 14” extension to the existing access frame is installed, sized as needed to preserve good access to existing utilities. This is straightforward to integrate with surrounding geofoam and pavers, and avoids the considerable cost of redoing all platform utilities.

Existing platform access stairs and ramps are extended within the existing footprint of the platform, with new railing installed as needed into the existing slab. Stairs require two more steps, and ramps require a 15-foot extension ramp running lengthwise along the platform to meet ADA regulations.

There will be cases where things get complicated, for example around the BART escalators and turnstiles at Millbrae. These may require special configurations with additional ramps and steps, but these problems will arise regardless of construction approach.

Step 5: EMU Step Removal

Once all remaining 8” platforms have been raised to 22”, the fixed step on the trains can be removed, restoring the EMU’s sleek exterior. The sensors on the gap filler steps can also be removed, as these now always extend and no longer need to detect platform height.

In conclusion, this construction sequence for level boarding will not cost $2 billion nor take until the late 2030s. It can be deployed in three years if Caltrain wants it badly enough. Here we hit upon an underlying problem, that their actions over the past decade imply they may not care for level boarding at all. This must change; let them not rest on their electrification laurels for too long.