Sarnia Road Bridge

Bridge Documented: August 5, 2006

This heritage bridge is at risk of demolition, although preservation is still on the table.

This beautiful pin-connected Pratt through truss bridge was built in the late 1890s from St. James, Manitoba and relocated to its current location in 1909, according to the heritage assessment for this bridge. The bridge has been closed to traffic, and this important heritage bridge is currently at risk for demolition, as its replacement is planned. Three alternatives are currently under consideration:

-A. Retain existing bridge close to it's current location.
-B. Relocate existing bridge.
-C. Remove existing bridge and complete full recording and documentation of existing bridge.

Historicbridges.org strongly believes options A and B are both highly feasible, and further believes that option C is so highly unacceptable that it should be dismissed immediately. The small size of the Sarnia Road Bridge and pin-connected design make the bridge an excellent candidate for being restored in-kind, which means the bridge is restored in a way that its original design is maintained and anything that can absolutely not be restored on the bridge be replicated. A true in-kind restoration would actually remove the floorbeams from the bridge which are not original and create the replicas of the original beams (based on either factual data or assumptions drawn from similar structures with integrity) which would have either been rolled American Standard Beams (as they were known in the United States) or built-up floorbeams.

When you first turned down Sarnia Street, you might think that a road as busy as it is could never have a one-lane pin connected through truss bridge on it. The five ton weight limit sign is the only thing that would suggest an old bridge was down the road. Nevertheless, here the bridge was open to a fair amount of vehicular traffic until its closure in 2008. It was highly unusual to see a one-lane pinned truss on such a busy road. However time finally caught up with this bridge after it suffered damage from somewhat less than intelligent truck drivers who disobeyed restriction signage and attempted to cross the bridge. Now the bridge's fate is uncertain, despite its obvious and verified heritage significance and feasibility for being relocated (or bypassed) and the recipient of an in-kind restoration for pedestrian use.

 The frist time this bridge was visited it was open to traffic and not uncommon to have a few cars lined up at either side to get across the bridge. With no stoplight to control traffic, the bridge is treated like a four-way stop, with each side taking turns. The wait time with a few cars ahead going across this bridge was less than that of the average red light on a stoplight. This bridge teaches a lesson to all the road commissions in Michigan who say that rural one-lane truss bridges that carry two cars an hour are unsafe. Here is a one-lane truss bridge on a paved suburban road with moderate traffic and no definitive traffic control device like a stoplight, and the bridge does its job fine, except for those trucks that disobeyed the restriction signage.

The historic society of Frankenmuth, Michigan once told historicbridges.org that in the old days, the Beyer Road Bridge had a wooden deck that was so loud when you drove across it that the noise could be heard for miles. One could never imagine what they were talking about until they experienced this bridge. When a car passed over the Sarnia Road Bridge, the wooden deck made an incredible racket, which almost hurt the ears while standing on the bridge. The bridge must be like an amplifier for the wood boards, which are loose on the deck.

The Sarnia Road Bridge is an 1890s pin connected Pratt through truss, and since 1909 has carried Sarnia Road over railroad tracks. As through trusses go, this is a short one, having only five panels. The top chord is unusual and interesting because there is v-lacing on both the top and the bottom. The end posts only have v-lacing on the bottom. Although this bridge carries vehicular traffic, some features of this bridge are more railroad-like in style. Railroads often were responsible for building highway over railroad overpasses. The main thing to note is that the v-lacing style is different. Often, railroad v-lacing does not share rivets with each piece of lacing. Instead, each end of v-lacing gets its own rivet. Also, the ends of the v-lacing are chopped off square, rather than having rounded ends. This style of v-lacing is typical of a railroad bridge. The large wood beams that make up the deck have a railroad-like feel to them also. On the other hand, the lightweight pin connected style of this bridge is something that is associated with vehicular bridges, not railroad bridges. In short, if you crossed a railroad truss bridge with a highway truss bridge, you would get the Sarnia Road Bridge. One final oddity to note about this bridge is that there is bracing rod that runs through the three middle panels of the truss. This can be seen in the photo of the bridge on this page. Having bracing in this area of the bridge in unusual.

Overall, this is an unusual bridge. It is also rare for the area, because pin connected truss bridges are in very short supply in southwestern Ontario. It is impressive to see a one-lane bridge open to a good amount of traffic. However, the time has come for this bridge to be protected from truck drivers and historicbridges.org hope that the bridge is restored for pedestrian use. If such time does come, the resources and communication network of historicbridges.org stand ready to assist London in learning how to relocate and restore this bridge, if London wishes to take advantage of them.