It’s mid-morning in Midtown Manhattan, and drivers are lined up to make a left turn when the light changes. They can’t. An illegally parked car, lights blinking, is blocking the turning lane, forcing drivers to create more traffic as they merge.

Where’s the traffic cop? Sigh: The abandoned car belongs to the traffic cop, who has been in the drugstore for a quarter-hour.

The absurdity is one tale from Mayor Bill de Blasio’s Midtown streets — and his new plan will make things worse.

A week ago Sunday, de Blasio announced his scheme. A big chunk of it is called “clear lanes.” The idea is to create new “moving lanes” on 11 crosstown streets, from 60th to 36th.

To do this, the mayor will add 150 new police and traffic officers. They’ll ticket for violations like double parking and blocking the box. The project may pay for its $10 million annual cost — but it won’t cut traffic.

Last week, I spent two days walking every inch of each of these 77 blocks. I found chaos so entrenched, it’s almost funny — and which can be fixed only with systemic change, not with de Blasio’s favorite trick: more government workers.

One indication of inevitable failure: The “clear lanes” zone is oddly gerrymandered. From 46th to 53rd Street, it extends to Ninth Avenue, but the 54th Street zone stops at Eighth.

Why? Hmmm. Between a courthouse and a police station, illegally parked cars, both marked vehicles and workers’ personal cars, litter the sidewalk and a lane.

That’s true of a carved-out block on the East Side, too. Someone had placed anonymous Xeroxes on personal cars warning their owners that “You are illegally parked.” Without a ticket, that’s a ratification of low-level public corruption, not a rebuke.

It’s also a reminder that adding more enforcement cars to traffic makes no sense: There’s no place to go. New traffic officers should work on foot or bicycle.

Another problem: construction. These 77 blocks contain 231 individual lanes — for travel, deliveries or quick commercial parking.

But I counted 30 of these lanes indefinitely closed for construction. That’s 13 percent of Midtown’s street space off limits.

And that figure actually understates the case. Construction lanes screw up the entire block, or nearly 40 percent of these 11 crosstown streets.

Construction lanes range from a demolition container taking up 50 feet to two whole lanes shut on almost an entire street. They range from a site with work actually going on, to a site blocked off for no discernible reason.

Drivers must merge unpredictably around them, sometimes multiple times on a block. This confusion creates blocked intersections for blocks behind, with no explanation. (It’s not the bike lane — there are none on crosstown streets.)

When the MoMA skyscraper under construction at 53rd and Sixth is receiving trucks, there’s no lane. Traffic just stops.

The closed-lane tally doesn’t include caravans of parked food trucks, mail trucks or trucks shredding documents — kitchen and office work in the middle of a crowded street.

Nor does it include the lane that Radio City will need all through Christmas season, which starts next week, to do security checks on “Christmas Spectacular” guests.

Nor does it include the card table that construction workers bizarrely set up smack at 47th and Sixth to do paperwork.

The streets, in sum, are a circus. As the holidays bring a crush of pedestrians, some of these cross streets that are already down to one narrow lane anyway should be closed to all but heavy deliveries.

One longer-term fix is to charge a fair price for construction lanes.

Developers pay only $50 to $135 per month to take a lane for months or years for a building project. No wonder they don’t care about inefficiency.

Charles Komanoff, a transportation economist, says the price caused by this congestion is closer to $12,000 a month per 100 feet.

De Blasio could charge fairly for this space as part of the congestion-pricing plan that Gov. Andrew Cuomo said he’ll announce next year. The city could use the money for street improvements.

But first, de Blasio has to decide: Is “clear lanes” a protection racket for the construction industry and for public employees, or is it to improve New Yorkers’ quality of life?

Nicole Gelinas is a contributing editor to the Manhattan Institute’s City Journal.