Just two days left until Seattle-area commuters must brace for all-electronic tolling on the Highway 520 floating bridge. If you can’t figure it out right away, no worries. You’ll have 40 years to get it straight. That’s how long it’ll take to collect half the $4.65 billion required to build a new six-lane bridge and roadway from Interstate 405 to I-5. The rest comes from gas taxes and yet-to-be-determined funding sources.Starting Thursday, most drivers crossing the bridge will pay up to $3.50 at peak hours from a windshield-mounted pass, which basically works like a debit card. Failure to ante up the correct amount will result in having your license plate photographed, and then a nice little bill will be sent to you for the toll and a $1.50 surcharge.Understandably, a good number of commuters are nervous that the new tolling system is going to clog the bejesus out of I-90, as drivers go out of their way to avoid the toll. And really, who can be sure this thing is even going to work?Technical problems pushed back the start of tolling for more than a year, meaning the state was out nearly a million bucks in anticipated revenue.Every weekday, some 30,000 cars per lane cross the bridge, setting up quite a challenge for the new electronic system. As Peter Samuels, editor of Toll Road News, tells the Seattle Times, “If it can be made to work satisfactorily there, it can be made to work anywhere.”