This week Mayor Bill de Blasio signed legislation requiring food carts to post letter grades the same way that restaurants do.

“I personally have never had anything from a vendor,” said the bill’s primary sponsor, Councilmember Karen Koslowitz of Queens. “Never, because I was never sure of the cleanliness.”

Koslowitz says that will change when the letter system hits the street carts near her. “I intend to have my first hot dog at a food vendor with an A.”

This is the premise — food safety through transparency — behind NYC’s restaurant grading system, enacted in 2010. Since then, most New Yorkers have become accustomed to looking for that A or maybe B.

Do you need ratings for your lunch falafel?

For officials like Koslowitz, the letter system will make street carts cleaner for hungry consumers. But there is some debate on whether the letters have actually made restaurants cleaner: The vast majority of establishments now get A’s, but some observers suggest the Health Department can be capricious in handing out their judgements. Some critics claim inspectors might grade on a curve, giving restaurants small violations that don’t knock them down by a full grade.

The health department counters by pointing to decreases in salmonella rates.

Many vendors welcome the proposed letters, says Sean Basinski, director of the Street Vendor Project, an advocacy group which has been supportive of the new law. It’s not exactly a top of mind concern, but he says the grades could give vendors “more legitimacy” in skeptics’ eyes. Yes, this heating surface is sanitary enough for the top grade — etc.

Basinski wanted to make it clear that the letters would be a change largely in what the public sees, and that little would necessarily change behind the scenes. Generally, food carts are held to the same standards as restaurants are, and vendors have to pass a pre-permitting inspection once every two years. That’s true from the lowly cart of nuts to the tricked-out vans that can go for $160,000 with equipment, according to Basinski. There are also unannounced city inspections of each mobile vendor at least once a year.

The Department of Health and Mental Hygiene is working on the details and criteria for the street vendor letter-grading system. The law gives them nine months. But one thing is clear already: the letters will only go to officially permitted food vendors. The number of permits are severely limited by law, a bone of contention to groups like the Street Vendor Project.

The grading system we need

Don’t expect to see grades for unpermitted vendors like the little two-wheel ice cream carts at Coney Island or the churro sellers by the subway on Roosevelt Avenue.

They, like the tamale carts and Italian ice hawkers, might fly under the radar, but that just goes to show that while the letter system may help guide your casual food cart user, the heavy user/strong-stomached New Yorker might want a more comprehensive grading system.

For example: Does the vendor remember to put napkins in the bag? (if not, 2 violations, and 3 for adding an unreasonable flurry of napkins)

Do they keep the line moving during the lunch rush? (if not, 1 violation)

Are they there for you after 10 p.m. when you missed dinner and are looking to spend $4 and be completely full? (bonus points; don’t worry about all the meat exposed to the elements)

If they’re lined up outside a big office building with ten other carts, do they have music to scare the other carts away? (points for trying)

Does a bottle of water/cup of coffee cost you anything other than $1? (five violations)

Will there always be that special shawarma cart with just the right hot sauce, free salad and donuts on Wednesday — a cart that’s better, you know in your heart, than even the featured stars on Anthony Bourdain? (yes/automatic A).