Is the City creating a dangerous situation by adding the extra lane section to the north side of the OR174?
Currently traffic from Blair Road on-ramp merges into the two west-bound lanes of the OR174. The traffic then travels in a steady flow until it reaches the off-ramp for the east-bound 417. More than 500 metres separates the on-ramp from the off-ramp, allowing drivers to change into the appropriate lane. Because there is no forced cross-over of lanes within a short distance, the traffic movements along this stretch of the OR174 would not be considered Weaving; there is a merge, and then later traffic diverges.
The City is planning to connect the Blair on-ramp to the east-bound 417 off-ramp with an additional lane. Since the OR174 east of Blair only has two east-bound lanes, this new third lane will be clear for the people entering from the Blair on-ramp; thus, the majority of people will likely stay in this clear lane instead of changing into a crowded lane. As the traffic in the new lane approaches the off-ramp for the east-bound 417, through traffic will be forced to merge into the more crowded lanes to the left. I believe that most people will try to stay in the clear lane as long as they can. This pushes the merge point very close to the divergence point for the 417. Traffic heading for the east-bound 417 will have the choice of moving right into the new lane earlier than the current start of the off-ramp, but many will not change lanes until closer to the exit. Now we have a crossing of vehicles in a short space; vehicles moving right to avoid exiting, and those moving right to leave the OR174. Now we have a Weaving problem. If the number of people leaving the OR174 is small, then this Weaving might be acceptable.
Now, assuming the MTO work is done before the NCC gets the Aviation Parkway dedicated to an inter-provincial Bridge link, or that the Inter-provincial Bridge goes in a different location, then the MTO plans to extend the St. Laurent off-ramp to meet the east-bound 417 off-ramp*. In this scenario, the traffic which wants to travel east on the 417 (i.e., the traffic leaving the OR174 at this interchange) AND the traffic which wants to exit onto St. Laurent boulevard or go to the Mall will all be diverging where the majority of Blair traffic is trying to merge. This will increase the amount of Weaving to the point of being a problem.
* For those who have not been following the MTO’s Plan, they plan to extend the St. Laurent off-ramp and segregate it from the 417/OR174 with a concrete barrier. This is to prevent vehicles from arriving along the 417 and exiting on the St. Laurent off-ramp. This handles their Weaving problem where vehicles need to cross several lanes of the 417/OR174 to get to the off-ramp.
If the Aviation Parkway is selected as the route to the new Inter-provincial Bridge, a new ramp from the Aviation Parkway will replace the St. Laurent off-ramp extension and there will no longer be an exit to St. Laurent from the east. People would use the Aviation Parkway to Ogilvie Road to get to St. Laurent Boulevard.
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