CEMP-E
TI 850-02
AFMAN 32-1125(I)
1 MARCH 2000
(5) Flangeways.
(a) General. These are often the most maintenance-intensive parts of a crossing. In all crossings,
a clear flangeway space must be provided to allow unimpeded passage of the flange on railroad wheels.
(b) Open or Closed Flangeways. Depending on the location, opinion may vary on whether the
benefits of filling a flangeway exceed its costs and disadvantages. Open flangeways allow water to enter
the crossing and track below, that is usually considerable highly undesirable; however if the drainage is
good, the water may quickly run off and cause little harm. Over time, dirt and debris entering an open
flangeway may impede drainage. Filled flangeways are often subject to rapid build-up of dirt and debris
or snow and ice. If left uncleaned, these foreign materials are typically packed in by the passage of wheel
flanges and may build up to the point of blocking the flangeway and causing a derailment. Ice in a
flangeway has a high probability of causing a derailment. In summary, an open flangeway readily allows
water to enter the track structure, and a filled flangeway must typically be cleaned more frequently. In
areas with low annual rainfall, or where track and road gradients naturally direct water away from the
crossing, an open flangeway design may be preferred. In most other cases, a filled flangeway will
provide long term benefits by reducing the amount of water entering the track through the flangeway.
(c) Filler Material. The least desirable filler is asphalt. While inexpensive, it tends to break in a
short time, losing its ability to seal against water entry, and ultimately requiring time-consuming removal
and replacement. Preformed or pourable rubber products are available for some crossings. Rubber
crossings typically come with a flangeway filler molded in as part of the panel. Concrete panel crossings
are often supplied with rubber flangeway fillers, sometimes pre-attached to the panels. Rubber fillers may
have a high initial cost, but they offer a reasonably good seal against water entry, are generally long
lasting, and have a flexibility that reduces the tendency of a debris-packed flangeway to cause a
derailment. Rubber flangeway fillers are especially useful where: (1) crossing geometry and low relative
elevation naturally direct rainwater to the crossing flangeways, (2) where crossing drainage is naturally
difficult, or (3) where crossing heave from freeze-thaw cycles is a common problem from rainwater or
snowmelt entering unsealed flangeways. Rubber fillers are also an alternative where asphalt filler has not
held up well in the past. Figure 7-11 shows rubber flangeway fillers installed in a concrete panel crossing.
Figure 7-11. Rubber Flangeway Fillers
7-13
Previous Page
