This is among the most dangerous places to cycle in Ottawa. The underpass at the CN bridge is so narrow that two cars can barely squeeze past each other. If there's also a cyclist present on this stretch of road, it's simply impossible. There are shards of car parts at the base of the bridge which shows that there have been accidents.
It can be difficult to avoid cycling under the bridge, as shown in the Routing section.
Have a look around Google Streetview to get a feel for this spot, from the east and the west.
There are signs on both sides of the bridge telling motorists not to pass bicycles.
Anecdotal evidence shows that this rule is frequently ignored. Here are some examples of what can happen:
When the cyclist takes the lane, which is the right thing to do, traffic has to slow down, which increases congestion and conflict with motorists.
Rebuilding the bridge to provide enough room for dedicated bike lanes is ideal but unlikely.
There are three practical solutions:
1. Larger signage on the bridge itself directing cars to yield to cyclists.
2. Stop signs or traffic lights to force traffic to go slower.
3. Reduced speed limit on this section of Carling