Harvard Bridge

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Charles River overpass

title: "Harvard Bridge" type: doc version: 1 created: 2026-02-28 author: "Wikipedia contributors" status: active scope: public tags: ["bridges-completed-in-1891", "bridges-in-boston", "historic-american-engineering-record-in-massachusetts", "landmarks-in-back-bay,-boston", "landmarks-in-cambridge,-massachusetts", "massachusetts-institute-of-technology", "massachusetts-institute-of-technology-student-life", "buildings-and-structures-in-cambridge,-massachusetts", "transportation-in-cambridge,-massachusetts", "bridges-in-middlesex-county,-massachusetts", "road-bridges-in-massachusetts", "1891-establishments-in-massachusetts", "bridges-over-the-charles-river", "steel-bridges-in-the-united-states", "girder-bridges-in-the-united-states"] description: "Charles River overpass" topic_path: "engineering" source: "https://en.wikipedia.org/wiki/Harvard_Bridge" license: "CC BY-SA 4.0" wikipedia_page_id: 0 wikipedia_revision_id: 0

::summary Charles River overpass ::

::data[format=table title="Infobox bridge"]

Field	Value
bridge_name	Harvard Bridge
image	File:2017 Harvard Bridge from Memorial Drive, Cambridge, Massachusetts.jpg
image_size	325px
caption	Harvard Bridge seen from Cambridge in August 2017
carries
crosses	Charles River
locale	Boston–Cambridge, Massachusetts, United States
maint	MassDOT
id	B160124EYDOTNBI
material	Steel
design	Haunched girder bridge
number_spans	25
piers_in_water	24
length	659.82 m (roadway)
364.4 smoots ± one ear (620 m) (sidewalk from Storrow Drive to Cambridge only)
width	21.13 m (total width)
15.8 m (roadway)
load	78.4 t
below	3.7 m
traffic	as of 2005
begin	1887
complete	1891
open	, 1990
closed	1983 (temporary closure for repairs)
coordinates
builder	Boston Bridge Works
::

Harvard Bridge, also known locally as the Massachusetts Avenue Bridge and "Mass. Ave." Bridge, is a steel haunched girder bridge carrying Massachusetts Avenue (Route 2A) over the Charles River and connecting Back Bay, Boston with Cambridge, Massachusetts. At 659.82 m, it is the longest bridge over the Charles River.

After years of disagreement between the cities of Boston and Cambridge, the bridge was built jointly by the two cities between 1887 and 1891. It is named for John Harvard, the founder of Harvard University. Originally equipped with a central swing span, it was revised several times over the years until its superstructure was completely replaced in the late 1980s due to unacceptable vibration and the collapse of a similar bridge in Connecticut.

The bridge is known locally for being marked off in the idiosyncratic unit of length called the smoot.

Conception

In 1874, the Massachusetts Legislature authorized construction of a bridge between Boston and Cambridge, and in 1882 follow-up legislation set out its location.

The bridge was to have a draw with an opening of at least 38 ft. Boston interests opposed the bridge, mainly because it did not provide for an overhead crossing of the Grand Junction Branch of the Boston and Albany Railroad. Further legislation in 1885 changed the draw to a clear opening of at least 36 ft and no more, until the other bridges below the proposed location were required to have a larger opening. There was still no substantive progress until 1887, when Cambridge petitioned the Legislature to compel Boston to proceed; the resulting act required each city pay half the cost, and allowed Boston to raise up to $250,000 (US$ with inflation) for this purpose, in excess of its debt limit. This implied an estimated cost of US$500,000 (US$ with inflation) for the bridge.

The Legislature provided for a bridge commission, to consist of the mayors of Boston and Cambridge plus a third commissioner to be appointed by the mayors. The mayors of Boston and Cambridge, Hugh O'Brien and William E. Russell, appointed Leander Greeley of Cambridge as the third commissioner, though this appointment changed over time.

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Year(s)	Mayor of Boston	Mayor of Cambridge	Third Commissioner
1887–1888	Hugh O'Brien	William E. Russell	Leander Greeley
1889–1890	Thomas N. Hart	Henry H. Gilmore
1891	Nathan Matthews, Jr.	Alpheus B. Alger	Leander Greeley (died February 15, 1891 or February 16, 1891{{cite web
::

The commission's 1892 report claimed:

Name

The bridge is named in honor of John Harvard, whose philanthropic gift was used to establish Harvard University. Other names suggested included Blaxton, Chester, Shawmut, and Longfellow.

Engineering

::figure[src="https://upload.wikimedia.org/wikipedia/commons/7/7a/Harvard_Bridge_postcard,_1910.jpg" caption="Maseeh Hall]], a dormitory at the [[Massachusetts Institute of Technology"] ::

::figure[src="https://upload.wikimedia.org/wikipedia/commons/d/d8/Harvard_Bridge_postcard_1920ish.jpg" caption="Cambridge]] and MIT"] ::

Originally projected as a wooden pile structure with stone pavement for the first 200 ft (because the Charles River Embankment extension was expected to take that space) the design was changed to be entirely iron spans on stone piers. The general plans were approved on July 14, 1887. The engineers were William Jackson (Boston City Engineer), John E. Cheney (assistant Boston City Engineer), Samuel E. Tinkham (assistant engineer), and Nathan S. Brock (assistant engineer at bridge).

The subsurface conditions at the bridge location are extreme. Much of Boston is underlain with clay, but the situation at the bridge is exacerbated by a fault which roughly follows the path of the Charles River itself. From a depth of approximately 200 to below existing ground, is a very dense till composed of gravel and boulders with a silt-clay matrix. Above that to approximately 30 ft below the surface is Boston blue clay (BBC). Over this are thin layers of sand, gravel, and fill. The BBC is overconsolidated up to a depth of approximately 70 ft.

The substructure originally consisted of two masonry abutments and twenty-three masonry piers, as well as one pile foundation with a fender pier for the draw span. The superstructure was originally twenty-three cantilevered fixed spans and suspended spans, of plate girders with one swing span. The Boston abutment rests on vertical piles, while the Cambridge end is directly on gravel.

Originally, the bridge was built across the Charles River connecting West Chester Park, in Boston, with Front Street, in Cambridge. This is now called Massachusetts Avenue on both sides of the river. As originally built, the total length between centers of bearings on abutments was 2164 ft with a draw 48 ft wide between centers. The width of the bridge was 69 ft except near and on the draw.

The bridge as built was composed of fixed and suspended spans roughly 75 ft long and piers 90 ft apart, center to center. The span lengths alternated between 75 and. The longer spans were cantilevered, while the shorter spans were suspended between the cantilevers.

The original roadway contained two lanes for horse-drawn vehicles and two street car tracks, for a total width of 51.0 ft. There were also two 9 ft sidewalks. The original roadway and sidewalk stringers were of wood, with an approximately 1.25 in thick covering of asphalt on the sidewalk and a 2 in spruce wearing surface on the roadway.

The exception was at the swing span, which was 48 ft wide. This span was approximately 149 ft long, and sat on a wooden pier. It was a double-cantilevered, electrically-driven structure also carrying a bridge caretaker's house.

The bridge opened on September 1, 1891. The original cost of construction was $511,000, $ in current dollars.

Maintenance and events

::figure[src="https://upload.wikimedia.org/wikipedia/commons/d/db/Harry_Houdini_jumps_from_Harvard_Bridge,_Boston,_Massachusetts,1908-_John_H._Thurston,stereopticons_LCCN2015650990-_restoration.jpg" caption="[[Harry Houdini]], who jumped from the bridge in 1908"] ::

In 1898, 3 ft bicycle lanes were installed next to each curb.

A marker near the southeast end of the bridge memorializes one of Harry Houdini's "well known escapes", during which he jumped from the bridge on May 1, 1908. (Other sources give the date as April 30, 1908.){{cite book |last=Clinger |first=Julia |title=It Happened in Boston |url=https://archive.org/details/ithappenedinbost00clin |url-access=registration |edition=1st |date=June 1, 2007 |publisher=TwoDot |isbn=978-0-7627-4134-2 |pages=61–63

The bridge was declared unsafe in 1909, requiring all of the iron and steel to be replaced. The draw was elevated slightly and the trolley rails were replaced as well.{{cite news | title = Famous Harvard Bridge Unsafe| url = https://timesmachine.nytimes.com/timesmachine/1909/07/16/101818048.pdf| work = New York Times | date = July 16, 1909 | access-date = March 20, 2012 | quote=The famous Harvard Bridge connecting Cambridge and Boston was declared to be unsafe in a report made to-day by a commission of Boston and Cambridge engineers, and announcement was made that work would be started on Monday next to strengthen the structure. The commission finds that all of the iron and steel beams of the bridge, which is nearly three-quarters of a mile long, will have to be replaced by new ones, at the same time the draw will be elevated slightly, and new surfacing will be put on. The Boston elevated railway company, which operates its cars across the bridge, is ordered to install new rails and new supports. }}

When the Metropolitan District Commission (MDC) took control of the bridge in 1924, they rebuilt much of the bridge superstructure. They replaced the wooden stringers with steel "I" beams, topped wooden deck elements with concrete and brick, and replaced the street car rails.

Heavy traffic at the Mass Ave and Memorial Drive intersection on the Cambridge end of the bridge led to the construction of an underpass in 1931.

The bridge was formerly referred to as the "Xylophone Bridge" because of the sound its wooden decking made when traffic traveled over it. This decking was replaced in 1949 with 3 in concrete-filled "I-beam lok" grating topped with a 2.25 in thick bituminous wearing surface. At this time, all bearings were replaced, and the trolley car tracks were removed, as were granite blocks. The trolley car poles were reused for street lights. Ramps between the bridge and the under-construction Storrow Drive were added.

The 1924 sidewalk slabs were replaced by precast, prestressed slabs in 1962.

Engineering study, 1971–1972

::figure[src="https://upload.wikimedia.org/wikipedia/commons/9/9e/Harvard_Bridge_Art.JPG" caption="Harvard Bridge is decorated with both serious and whimsical works of art."] ::

An engineering study was performed by the Metropolitan District Commission (later merged into the Department of Conservation and Recreation) in 1971–1972 due to complaints by bridge users of excessive vibration. The bridge was found to be understrength for its load. Before the final study was complete, the recommendation was to place a load limit of 8 ST per axle and a total of 15 ST per vehicle, or to restrict trucks to the interior lanes, where the bridge was stronger. A 25 ST limit was imposed.

Suggestions made included strengthening the existing structure by adding either struts or plates to make the existing four beams along the length of the bridge into a stiffening truss, or to replace the superstructure with a new one, made of either steel or concrete, which would be up to current standards. The recommendation was to replace the superstructure with one weighing approximately the same in order to reuse the piers, which were in good condition.

The reasoning was that the cost of a new structure could be predicted much more easily than the cost of repairing and reinforcing the existing bridge. The resulting new bridge would be of known materials and quality, such as ductile structural steel rather than brittle wrought iron, and rated at AASHO HS-20. Repairing the existing structure would leave old wrought iron of uncertain quality and condition standing, and would not bring the design up to (then) current standards. The price was estimated at US$2.5 million to US$3 million (US$ to US$ with inflation).

The action taken based on this study was to establish load restrictions on the bridge, 15 ST in the outer lanes, 25 ST on the inner lanes. This was expanded in 1979 to a flat limit of 15 ST on the whole bridge.

Superstructure replacement, 1980s

After the failure of the Mianus River Bridge at Greenwich, Connecticut in 1983, the Harvard Bridge was shut down and inspected because it contained similar elements, specifically the suspended spans.{{cite news | last = Keane | first = Tom | title = It's the Engineering, Stupid | work = Boston Globe Magazine | publisher = Boston Globe | date = September 10, 2006 | url = http://www.boston.com/news/globe/magazine/articles/2006/09/10/its_the_engineering_stupid/ | access-date = September 11, 2006 |archive-url=https://web.archive.org/web/20061031060417/http://www.boston.com/news/globe/magazine/articles/2006/09/10/its_the_engineering_stupid/ |archive-date=31 October 2006 }}{{cite news | agency = United Press International | title = AROUND THE NATION; Boston's Harvard Bridge Closed to Heavy Trucks | work = The New York Times | date = July 6, 1983 | url = https://www.nytimes.com/1983/07/06/us/around-the-nation-boston-s-harvard-bridge-closed-to-heavy-trucks.html | access-date = April 13, 2009 }} Traffic was restricted to the inner two lanes due to the discovery of two failed hangers on span 14. A few days later, all trucks and buses were banned from the bridge.

In 1986, a report was published containing the plan to replace the superstructure on the existing supports. Alternatives considered were very similar to the 1972 report, and were similarly decided. Structural modifications included an upgrade from four longitudinal girders to six of the same shape and replacement of a stairway with a handicapped pedestrian ramp on the Boston end of the bridge.

Ramp "B", from southbound (Boston bound) bridge lanes to eastbound Storrow Drive, caused traffic to merge onto Storrow Drive from the left (high speed) lanes using a short acceleration lane, causing safety issues. The MDC requested elimination of this ramp. Compared to overall bridge traffic of 30,000 vehicles per day, traffic on ramp B was found to be low, approximately 1,500 vehicles per day with a peak of 120 vehicles per hour.

The historic value of the bridge was considered significant, so the plan was to make the replacement superstructure appear similar, with similar railing and lighting. In order to document the pre-existing structure, a Historic American Engineering Record (HAER) would be prepared.

Pier 12 was exhibiting inappropriate movement and was scheduled for reinforcement.

The work would be done in two phases. Phase 1 would reinforce the downstream side of the bridge to allow MBTA bus traffic, and was expected to take 5 months. Most of this effort would be spent on the underside of the bridge and would not affect existing traffic. Phase 2 would replace the entire superstructure and was expected to take three construction seasons to implement. Cost was estimated to be (US$ with inflation). Phase 1 finished in 1987, and Phase 2 in 1990.{{cite news | title = MASS. AVE. BRIDGE TO REOPEN FOUR LANES AFTER SEVEN YEARS | author = Ronald Rosenberg, Globe Staff | newspaper = Boston Globe | location = Boston, Massachusetts | date = September 12, 1990 | page = 35 (METRO section)

File:Harvard Bridge, Spanning Charles River at Massachusetts Avenue, Boston ( Suffolk County, Massachusetts).jpg|Bridge viewed from the upstream Cambridge side in 1985. Construction barrels restricting traffic from the outside lanes, and general wear and tear are visible (click on image to enlarge) File:Harvard Bridge from Cambridge, 2009.jpg|Roughly the same view, in 2009. Superstructure is in much better shape only 20 years after completion, than the 1985 superstructure was roughly 40 years after its most recent major work. File:Underside, centerline, 1985.jpg|Underside of the bridge in 1985. Image shows how the bridge was originally built, and later modified, but before the superstructure was replaced. File:Harvard Bridge, centerline, looking north, 2009.jpg|Underside of the bridge in 2009. Image shows how the replacement superstructure was built, with six longitudinal girders, different bracing, etc.

Subsequent events

In the fall of 2014, the Charles River Conservancy announced that an anonymous donor would fund an upgrade of the street lights for both the roadway and both sidewalks on the bridge. The new roadway and aesthetic lighting was installed in 2015, highlighting the smoot marks along the sidewalk. The design was selected after a competition won by Miguel Rosales of Rosales + Partners.{{cite news | last = Ramos | first = Nestor | title = $2.5 million gift will shed light on the Harvard Bridge | work = Boston Globe | publisher = Boston Globe | date = October 14, 2014 | url = https://www.bostonglobe.com/metro/2014/10/13/call-smoot-lighting-million-gift-will-brighten-mass-ave-bridge/5UehpL7Zk7YV9gWB3hb3KP/story.html | access-date = October 22, 2014}}{{cite news | title = With Smoot design, Harvard Bridge is the latest to shine | work = Boston Globe | publisher = Boston Globe | date = October 21, 2014 | url = https://www.bostonglobe.com/opinion/editorials/2014/10/20/with-smoot-design-harvard-bridge-latest-shine/wjmtXBm32Zlt7ndXm9LHhO/story.html | access-date = October 22, 2014 }} The light posts were located 30 sm apart. "It will provide safe lighting for pedestrians and drivers, and the elements of design on the bridge will be pulled out and emphasized. It will become a really beautiful bridge," said Renata von Tscharner, founder and president of the Charles River Conservancy.

Separated bicycle lanes

In November 2021, to improve bicycle safety, MassDOT initiated a separated bicycle lane pilot on the Harvard by placing cones to create two wide bicycle lanes. This reduced general purpose lanes from four to two over the bridge. Despite some hiccups involving vandalism, the pilot was deemed a success in the Fall 2022. MassDOT went on to hire Toole Design Group to engineer flex-post separated bicycle lanes, bus priority lanes, and new traffic signal phasing for the corridor. These changes were implemented just before 2023, and have been in place since. To this date, the Harvard Bridge remains one of the most popular cycling routes in New England, with an average of over 1,000 bicyclists in each direction per day.

Smoots

Main article: Smoot

::figure[src="https://upload.wikimedia.org/wikipedia/commons/c/c8/Smoot_mark_210,_east.jpg" caption="Smoot mark 210 on the eastside of the bridge"] ::

The Harvard Bridge is marked off in an idiosyncratic unit of measure, the smoot.

In 1958, members of the Lambda Chi Alpha fraternity at MIT measured the bridge's eastern sidewalk by using that year's shortest pledge, Oliver Smootnominally, 5 ft tallas a measuring stick. Years after this stunt, Smoot became president of the American National Standards Institute (ANSI), and later president of the International Organization for Standardization (ISO).

Markers painted at 10 sm intervals give the bridge's length 364.4 smoots long, "plus one ear". Originally this read "plus or minus one ear"representing measurement uncertaintybut over the years the words "or minus" disappeared.{{cite web | url = http://web.mit.edu/newsoffice/2009/smoot-0604.html | title = Smoot in Stone | date = June 4, 2009 | work = MIT News | publisher = Massachusetts Institute of Technology | location = Cambridge, Massachusetts | access-date = July 20, 2010 | quote = Specifically noting the bridge's length of 364.4 Smoots (+/- 1 ear), the plaque, a gift of the MIT Class of 1962, honors the prank's 50th anniversary.

During the major reconstruction in the 1980s, the new sidewalks were divided into smoot-length slabs rather than the standard six feet, and the smoot markings were painted on the new deck.{{cite news | first = David A. | last = Fahrenthold | title = The Measure of This Man Is in the Smoot | url = https://www.washingtonpost.com/wp-dyn/content/article/2005/12/07/AR2005120702328_pf.html | newspaper = The Washington Post | location = Washington DC | date = December 8, 2005 | access-date = April 20, 2009 | quote = And then there was a little help from the government: When the bridge was renovated about 15 years ago, officials agreed to let the markings stay, even going so far as to score the sidewalk at 5-foot-7 Smoot intervals instead of the usual six-foot ones. | url =http://web.mit.edu/newsoffice/1999/hacks-0901.html | title =Keyser describes his top five hacks - MIT News Office | first =Denise | last =Brehm | date =September 1, 1999 | work =MIT News | publisher =Massachusetts Institute of Technology | location =Cambridge, Massachusetts | access-date = March 4, 2012 | quote =When the bridge was rebuilt in the 1980s, the Cambridge police requested that the smoots remain because they use them to indicate precise locations in accident reports.

The nominal length of 364.4 smoots (from two designated points at the bridge's ends) corresponds to about 2030 feet or 620 m, somewhat less than the bridge's published length of 660 m. corresponds to 387.7 smoots ± one ear.

References

Informational notes

Citations

Bibliography

(Nationalbridges.com): Note: this is a formatted scrape of the 2009 official website, which can be found here for Massachusetts:
{{citation |last1=Alger |first1=Alpheus B. |last2=Matthews |first2=Nathan Jr. |title=Harvard Bridge: Boston to Cambridge, March 1892 |url=https://books.google.com/books?id=1qQJAAAAIAAJ |access-date=April 10, 2009 |year=1892 |publisher=Rockwell and Churchill |location=Boston, Massachusetts
(Replacement): {{cite book |author=United States Department of Transportation, Massachusetts Department of Public Works |title=Harvard Bridge/Massachusetts Avenue Bridge over the Charles River, Bridge replacement project, Environmental Assessment |date= October 27, 1986 |publisher= The Administration |location=Washington, D.C. |id=
{{cite book |last=Leet |first=Kenneth M. |title=The Harvard Bridge, phase 2 report |date=July 7, 1972 |publisher=Metropolitan District Commission |location=Boston, Massachusetts |id=
{{cite book |last=Leet |first=Kenneth M. |title=The Harvard Bridge, final report phase 3 |date=October 1972 |publisher=Metropolitan District Commission |location=Boston, Massachusetts |id= |page=1

References

"Harvard Bridge".
[[Department of Conservation and Recreation]] [[National Bridge Inventory]]. (2012). "Place Name: Boston, Massachusetts; NBI Structure Number: 417208078401120; Facility Carried: Route 2A; Feature Intersected: Charles River". Nationalbridges.com (Alexander Svirsky).
Massachusetts Commissioner. (1892). "Harvard Bridge Boston to Cambridge". Rockwell and Churchill.
HAER, p. 3
Kaiser, Johanna. (January 6, 2012). "Mass. Ave, BU Bridge bike lanes completed". New York Times Co..
(October 3, 1924). "Commonwealth Begins Work on Harvard Bridge". [[Massachusetts Institute of Technology]].
HAER, p. 5
The fifteen expansion dams were replaced or repaired in 1969.HAER, p.6
Leet, phase 3
Detailed engineering calculations were included.Leet, phase 3, appendices
HAER, p.8
Replacement, p.7
Replacement, p.4
Replacement, page 4-6
Replacement, p.11. Note the use of the HAER document throughout this article.
Replacement, page 5
"Smoot lighting: $2.5 million gift will brighten Mass. Ave. bridge - Metro - The Boston Globe". BostonGlobe.com.
"$2.5 million gift will shed light on the Harvard Bridge". Thecharles.org.
"Smoot Lighting to Set the Mood on Harvard Bridge".
"Smoot legacy continues on Harvard Bridge - The Tech". Tech.mit.edu.
(September 2, 2014). "An Anonymous Donor Is Bringing Light to the Mass. Ave. Bridge". Bostonmagazine.com.
"An Anonymous Donor is Bringing Light to the Mass. Ave. Bridge". Thecharles.org.
"Oliver R. Smoot". American National Standards Institute (ANSI).
[[Robert Tavernor. Tavernor, Robert]], ''Smoot's Ear: the Measure of Humanity'' (Yale University Press, 2007; paperback edition 2008), {{ISBN. 978-0-300-12492-7, Preface
{{sfn. Alger. Matthews. 1892. 659.82. m. ft

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