This is due to tight clearances under the bridges.

The 4DD was somewhat unsuccessful because the upper level compartments were cramped and poorly ventilated (the upper level windows could not be opened due to tight clearance).

However, it was not a "high-pressure oil" system based on shell bearings and tight clearances that we are familiar with, but a drip feed to roller bearings.

The F-units did have grab irons and stirrup steps, but these features were a hindrance in locations with tight clearances.

Special rules for evacuation of passengers are in place due to the tight clearance in the tunnel.

Twister roller coasters often have the illusion of having small or tight clearances due to the track usually travelling through several support structures.

There has been some discussion of preserving the railway however the tight clearances and light construction of the line would be a problem.

For one thing, the use of a wrecker's ball on a crane, a standard demolition tool in many locations, is not permitted in the city because of tight clearances.

This system was used by BMW until 1969, when they adopted the "high-pressure oil" system based on shell bearings and tight clearances, still in use today.

The "lc" in the model designation stands for "low clearance" as these locomotives are designed to negotiate the tight clearances under the mine equipment.