| has gloss | eng: Conceived by Oliver Bulleid for the Southern Railway's Dartford commuter route, the two 4DD electric multiple units were the only double-deck trains to run on the main line railway network in Britain. The upper-level seats were squeezed in between the lower-level seats to ensure that the overall height of the unit was within the clearances necessary to pass through tunnels and under 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). The compartments were pressure-ventilated but the equipment proved to be troublesome. Also dwell times at stations were increased because of the increased number of passengers per door. To obtain the extra seating capacity that was being sought, it was instead decided to lengthen trains from eight cars to ten. |
| has gloss | eng: Conceived by Oliver Bulleid for the Southern Railway's Dartford commuter route, the two 4DD electric multiple units were the only double-deck trains to run on the main line railway network in Britain. Whilst common in Europe and North America the restrictive railway loading gauge in the United Kingdom prohibits normal double-deck cars with two fully separated decks. On the 4DD carriages the upper-level seats were squeezed in between the lower-level seats to ensure that the overall height of the unit was within the clearances necessary to pass through tunnels and under 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). The compartments were pressure-ventilated but the equipment proved to be troublesome. Dwell times at stations were lengthened because of the increase in the number of passengers per door. To obtain the extra seating capacity that was being sought, it was instead decided to lengthen trains from eight cars to ten. |
| lexicalization | eng: SR Class 4DD |
| instance of | c/British Rail electric multiple units |
