How can a two-lane bridge replacing a two-lane bridge possibly be an improvement or fix a perennial summertime traffic situation?
Some readers chiming in on the news of the $12.5 Vedder Bridge were asking that very question.
The Chilliwack Progress turned to the engineering department at City of Chilliwack for some answers.
Why was a two-lane bridge design chosen?
Ok right off the bat, four lanes might seem better than two at first glance and four lanes would increase capacity at the site. But it’s also twice as expensive, and didn’t make sense on several levels, said staff.
One of the reasons why it was rejected is that FVRD and Ministry of Transportation officials have stated that a section of Columbia Valley Highway, from the traffic light to up past the lake near the U.S. border in Columbia Valley, is set to remain a two-lane road for the foreseeable future. So it wouldn’t make sense to make the bridge four lanes, only to be reduced down to two at the traffic lights. So the thinking went, unless it’s connected on either side by a four-lane roadway, it did not make sense to go that way.
So it clearly was not considered a sound or even reasonable economic investment to choose the four-lane option, and it was rejected before the design stage.
Secondly it turns out what effectively slows down traffic to a crawl on the existing bridge, especially in summertime, is not solely the fact that it’s a two-lane structure.
Rather city staff pointed out what is in fact constraining capacity is three-fold: the geometry of the existing bridge, the narrow lane width and the three-way stop at Chilliwack Lake Road.
The new Vedder Bridge will fix all three of those constraints.
The existing lane width is critically narrow at 2.9 metres each. The new lane width will be 3.5 metres, meaning the new bridge will be at least a metre wider, which is a little more than three feet wider.
Also the geometric kinks in the existing bridge alignment will be straightened out when the new bridge is built just downstream of the old one.
And finally, replacing the three-way stop at Vedder and Chilliwack Lake Road will be much more efficient. A single-lane roundabout will keep the traffic moving smoothly and steadily, in a way the stop signs never could.
Also important to know is that the engineering work is underway for the redesign of Vedder Road from Chilliwack Lake to Watson/Promontory, which constitutes the approach to the new bridge from the north.
Officials are in the middle of road design assignment but it is anticipated that Vedder Road from Keith Wilson to Watson will be widened to five lanes in that section, with four moving lanes and a centre turning lane, said staff.
The section from Keith Wilson to Chilliwack Lake Road will taper to two lanes, one in either direction with the southbound lane leading to the single-lane roundabout.