I have a plan at work showing the last few years worth of rebuilding the 401 from Renforth Drive through to Leslie Street. For nearly that entire length an extra lane has been engineered into the existing right of way in each direction. As was noted earlier in this thread, the 401 through the 427 interchange used to be 3 through lanes, it is now 4. As noted just above, the last stage of this rebuilding program is adding a third lane in the collectors through the Yonge/Bayview area.
Between 409 and the 427, the 401 does need another lane in each direction, but a widening through there is not in the cards at this point. A rebuilt Kipling Avenue bridge will likely be required to make that happen, but more certain is that a difficult widening over Dixon Road and Martin Grove and some expropriation along the north side will make for a very expensive project here one day.
Out in the burbs, the idea with the widenings is to taper the merger of lanes a little more gradually than the current sitaution.
In Mississauga, 401 westbound goes from 11 lanes approaching 403/410, to 4 lanes approaching Hurontario, to 3 lanes therafter. That area is the biggest traffic bottleneck in the entire province. I believe that the intention with the more gradual taper after reconstruction will be to take 7 lanes to Hurontario, 6 lanes to Mavis, and 5 lanes through the Credit Valley to Mississauga Road and 4 lanes to Winston Churchill Boulevard. Another lane would be added west of the 407 interchange to take it to 4 again out towards Milton. Similar windering would take place on eastbound lanes. All of that will take several years, and is on hold until the Hurontario and McLaughlin Road bridges are rebuilt. An EA is ongoing too.
Expansion will take place through Durham too. Plans have to be finalized regarding the location of 401/407 connectors before widening will take place east of Salem Road.
That's all I know right now.
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