Friday, November 28, 2014

Summer St. Bridge, Boston

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The southernmost of the four Fort Point Channel bridges we're covering is the Summer St. Bridge, built circa 1899. It's not terribly photogenic, but it's considered historic anyway due to its unusual design. Instead of a drawbridge that raises, or a swing span that pivots, the Summer St. bridge is a "retractile draw", which opens by sliding diagonally back and off to one side. Or both sides in this case, since it's a "double retractile" design. (Strictly speaking it doesn't open at all now, since it's unreachable by large vessels due to the fixed-span Moakley Bridge north of here.)

The Library of Congress collection of vintage photos of it; unfortunately none of them show the bridge in an open position, but an aerial photo makes it somewhat easier to visualize. Their info page about the bridge has a brief description, at least:

Significance: The Summer St. bridge is a rare movable type of bridge known as a retractile draw, in which the moving span is pulled diagonally away from the navigable channel on several sets of rails. Only four of these have been identified in the country, two of which are on Summer St. in Boston. The form is thought to have been invented by T. Willis Pratt in the 1860's. This bridge is a double retractile: parallel spans pull away from the center in opposite directions. Despite its deteriorating condition, the bridge is the center element of the rich Fort Point Channel Bridge District. / The Summer Street Retractile Bridge is the only known surviving electrically-operated, paired-leaf oblique retractile drawbridge. Despite its poor condition and loss of much of its operating equipment and auxiliary structures (gates, Tender's House, and pedestrian waiting shelters), several of the early components (superstructure, retractile rails, wheels, and operating machinery on the south side) remain. The Summer Street Retractile Bridge is one of five surviving movable bridges located in the proposed Fort Point Channel Historic District. It is one of eight known remaining nineteenth-century movable bridges in the Massachusetts Highway Department Historic Bridge Survey.

This bridge was the site of a 1916 streetcar disaster, in which a streetcar plunged off the open drawbridge into the channel, killing 47 people. Which is more or less what happened in Cleveland's Central Viaduct streetcar disaster two decades earlier. The accident here was blamed on operator error, compounded by poor signage & signals that were supposed to indicate when the bridge was open, but failed to get the driver's attention.

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