Solid bridge railing -- Solid bridge rail should be used only where the bridge superstructure is in no danger of overtopping. A solid type of rail (e.g., a parapet wall) is useful from a safety standpoint but constitutes a significant impediment to flood flow.

Open bridge railing -- The most desirable type of rail for accommodation of flood flow offers the floodwater an opening. An open slender type of bridge railing has a lower backwater and reduced lateral forces than a more solid type. A TxDOT research project was initiated to determine which of the standard TxDOT rails are the most hydraulically efficient. Results from this project are documented in a report, Hydraulic Performance of Bridge Rails ( ).