The ExpressLanes project in the L.A. area has been mildly controversial at times — the one-year experimental program is converting about 25 miles of existing carpool lanes on the 10 and 110 freeways into variable toll lanes. Carpoolers will still use the lanes for free and single motorists will be able to use them for a toll, when there’s sufficient space in the lanes to sell.

It’s a big step for both Metro and the Southland, which has always emphasized the “free” in “freeway.”

But it’s a modest step when compared to the toll lane program sought by the Bay Area-based Metropolitan Transportation Commission, which this week is seeking permission from the state to add 290 miles of variable toll lanes either by converting existing HOV lanes or widening freeways and adding new lanes.

That’s on top of the 280 miles of lanes already approved for conversion into variable tolls lanes. The region would like one day to have a whopping 800-mile network of the lanes.

As the map shows, the lanes that the MTC needs approvals for this week are mostly in the East Bay — an area that has relentlessly sprawled outward over the decades. Reading deeper into the MTC’s application, it also looks like many of the carpool lanes will in the future require three passengers for free use of the lanes. I’m guessing that won’t sit entirely well with everyone.

I’m unaware of any congestion pricing project this big in the U.S., although there are certainly some large metro areas such as New York and Chicago where tolls — for everyone — are routine on many roads. The Bay Area proposal is a different type of beast, given it’s targeting just the carpool lanes. It will be mighty interesting to see how well it works, how many people carpool or pay to use the lanes and, of course, whether the new toll lanes can speed up express bus service that uses freeways.