Hybrid rail is a newer form of rail transit combining characteristics of light rail and commuter rail. The development of hybrid rail is prompted by the desire to use smaller, lighter weight (light rail or streetcar like) diesel multiple unit rail vehicles on railroad corridors. Traditionally, federal regulations require the use of heavier trains (FRA compliant) on railroads due to safety concerns of heavier trains colliding with lighter weight trains.
Earlier hybrid rail systems either use non-FRA compliant vehicles on shared railroad tracks with time separations (freight trains running at night when there's no passenger service), or go with heavier FRA compliant multiple-unit vehicles. In recent years, federal laws changed to permit lighter weight passenger trains (FRA alternative compliance), and require the use of positive train control to prevent train collisions.
As regulations, adoptions, and technologies continue to evolve, the definition of hybrid rail and distinction from similar modes like light rail and commuter rail are likely to evolve as well. Prior to the addition of the mode by the USDOT, currently classified hybrid rail would fall under either light rail or commuter rail.
Characteristics of hybrid rail:
- Use of smaller and shorter multiple-unit vehicles similar to light rail, with smaller impacts compared to locomotive haul trains.
- For non-FRA compliant and FRA alternative compliant systems, they can use off-the-shelf train designs common in Europe with proven service records.
- Reduced noise, vibration
- Faster acceleration
- Reduced operating costs
- Allow more service during off-peak times when ridership doesn't justify use of longer locomotive haul trains. Limited or no off-peak service is a common characteristic for many commuter rail systems.
- Ability to share corridors or tracks with freight trains and/or locomotive haul passenger trains, reducing infrastructure costs.
As hybrid rail systems are recently built, they feature level boarding at all stops for all doors.