CBC traffic reporter Doug Hempstead describes how to steer clear of 417 closure

This weekend's closure of a downtown section of the 417 features one of the most complicated detours we've seen for a so-called rapid bridge replacement so far.

Crews have already constructed a brand new Percy Street bridge that's sat completed on the north side of the Trans-Canada Highway since the summer, waiting to be swapped out for the old one. The project has been delayed twice since August.

Percy Street runs under the 417 between Bronson Avenue and Lyon Street, but the closure to make room for this switcheroo involves a much longer section of highway than you might think.

Not only that, but we're not entirely sure how long the process could take. That depends on rain, but more about that later.

The 417 will be closed both directions downtown. The simpler of the two directions is westbound.

Westbound route

Traffic will be forced off the highway at the Catherine/Metcalfe exit near the Museum of Nature, then funnelled along Catherine Street six blocks before rejoining the highway via the ramp immediately after the Bronson intersection.

Those taking that route will get a pretty good view of the work being done, which means traffic will move slowly. Avoid this way if you're looking for an efficient workaround.

Remember, this is the Trans-Canada Highway. People will be detouring here who had no intention of getting off the highway in our fair city. Those of us who live here should use our local knowledge to give the detour a wide berth.

For example, if you live in Orléans and you're headed into Lowertown or Centretown, take the Sir George-Étienne Cartier Parkway from St. Joseph Boulevard all the way to Sussex Drive.

If you're headed into Ottawa's west end to visit IKEA, Bayshore or even a Sens game at the Canadian Tire Centre, use Hunt Club Road.

As long as you're not using the highway during peak periods (6:30 a.m. to 9:30 a.m. and 3 p.m. to 6:30 p.m.), you're safe to head westbound as far as Vanier Parkway/Riverside. During peak periods, the westbound 417 is going to be backed up to the 174 split, if not further.

A vacant stretch of Highway 417 pictured during a previous closure to allow for the replacement of the bridge over Booth Street. (Francis Ferland/Radio-Canada)

Eastbound route

Now, for the eastbound. This is where it gets ugly.

The detour in this direction is much longer — perhaps the longest ever for a rapid bridge replacement. Traffic will be forced off the eastbound 417 at Carling Avenue. It will then funnel east along Carling past several sets of traffic lights, past the Westgate mall, Civic hospital, Dow's Lake and all the way up to Bronson Avenue on the edge of the Glebe.

From here, detouring traffic will turn right and travel several more blocks down past Carleton University to the ramp for eastbound Riverside (not that anyone refers to it as eastbound, seeing as it takes you north).

Detouring traffic continues along Riverside Drive all the way back up to the 417. During peak periods with no highway closure this 12-km detour route would take you half an hour to complete. Goodness knows what it will be like during the closure.

It's not something you should try, unless you really enjoy gridlock.

Oh, and there's a high chance of rain Friday and a 60 per cent chance of rain again on Saturday and Sunday. The rain alone would make travel slow.

So, if you're in the west end and you need to go to Orléans, take Hunt Club Road.

If you're in the west end and you need to go downtown, take the Kichi Zībī Mīkan or Carling Avenue, but don't go further east on the 417 than the Woodroffe exit. And, if you're planning to do this during peak periods, just forget about the 417 altogether. Program your phone or navigation device for "fastest route" and "avoid highways."

Finally, we were originally told the project would be complete by 6 a.m. Tuesday, meaning four peak-period commutes. There was a chance it could be done early Monday, but if we get the forecasted rain, that seems unlikely.

For more information, follow my live traffic reporting on CBC Radio's Ottawa Morning from 5:30 a.m. to 8:40 a.m. and All In A Day from 3 p.m. to 6 p.m.