It turns out that last summer's initial assessment that there is enough capacity within the existing street network to handle traffic disruptions created by LRT was far too rosy.

At least for some key sections in Hamilton's west end.

LRT co-ordinator Paul Johnson says the project team now believes it will have to add an extra traffic lane on both Dundurn Street and York Boulevard — likely at the expense of existing bike lanes.

The big challenge, Johnson says, is to accommodate the displaced flood of westbound traffic that currently uses King Street West to get to the eastbound and westbound Highway 403 ramps and into west Hamilton and Westdale.

"We don't have all the solutions but we've really boiled it down to there are some areas when you can't use mitigation strategies (such as traffic signals)," Johnson said in an interview.

"You actually are going to have to go to extra lanes of traffic."

It's easy to grasp why when you consider how traffic currently flows.

Imagine it's rush hour and you're on King West in the thick of five lanes of westbound traffic at the busy Dundurn Street intersection.

When the light goes green, some cars turn left onto Dundurn, travelling south. Others cross the intersection, peeling left into the Dundurn/Fortinos plaza.

A significant number also exit left on to the westbound 403 ramp up the Ancaster hill and on to Brantford.

Meanwhile, the rest of traffic is either turning right onto the eastbound 403 ramp or continuing straight into west Hamilton or Westdale.

It's plenty busy but it generally goes down as smooth as a vintage port wine.

Until LRT arrives, that is. Then the current five westbound traffic lanes will be reduced to one. The others will be given over to an eastbound lane and the two side-by-side centre-running LRT tracks, one travelling east, one west.

That brings us back to the extra lanes on York and Dundurn.

The loss of westbound traffic capacity on King means drivers will need to be shifted to Cannon Street and York (Cannon becomes York at Queen Street). Drivers can then travel south up Dundurn, turning right on King to access the 403 ramps, or continue on to Aberdeen Avenue.

But York and Dundurn, as currently configured, are incapable of handling the extra volume of westbound traffic. Thus the need for an additional traffic lane on both those roads.

Where's the space going to come from? Good engineering, says Johnson, and a "review" of the existing bike lanes. In other words, the roads won't be widened, they'll be rejigged and reclaimed for cars.

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The problem is, the volume of traffic increases as you move west in this city, Johnson says. The "vast majority" of that volume is from the centre of the city to the 403, particularly the westbound ramp to Ancaster and Brantford.

"Somewhere around Bay it starts to get bad and it continues to get worse as you go westbound and then, unfortunately, we have to get everybody south to get onto that highway."

It doesn't help that King between the 403 and Queen Street is also a truck route, as is Queen itself. To adjust to the space taken up by LRT, Johnson says the north-west corner of Queen can be cut away to accommodate the turning radius of even the biggest truck.

But that still leaves big rigs barrelling down the one remaining westbound lane on King right next to a sidewalk. Johnson shakes his head over that. "We're still evaluating the truck route scenario," he says.

The final west-end challenge is at McMaster University, where capacity needs to be maintained to handle eastbound cars coming off Cootes Drive and Main West from Dundas. Again, it's cycling that will likely suffer.

Previously, the project team thought there was enough capacity on Main West to squeeze in some bike lanes. Johnson says they're now "rethinking" that.

All these challenges will be detailed at three public open houses this week. In mulling them over, it's perhaps worth bearing in mind Johnson's own assessment of LRT planning.

"Everything on this project is not what's perfect," he says, "it's what's optimal."