According to one of the first results I found, the deflection of Thriebeam is about 0.6 m. MTO uses 0.9 m for traditional W-rail, and 0.3 m with a channel. So it's kind of a thin margin that Thriebeam falls in between a standard rail and a fitting it with a channel.Segment of rail both with and without channel:The other advantage of using Thriebeam is the increased surface area, which helps in areas with significant heavy vehicle volumes.I can't speak for other jurisdictions, for retrofits, MTO will tend to go with the channelized rail. For new build, MTO handles it in their typical overkill fashion:
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