In cities with a lot of foot traffic, food trucks and carts have become almost as common a sight as fire hydrants, with many offering high-end cuisine for people in a hurry. And while these mobile restaurants are held to the same standards as brick-and-mortar locations, not all have been able to meet them.

According to the Los Angeles Times, 27 percent of food trucks in Los Angeles earned less than an “A” grade from city health inspectors. That means more than 10 points were taken off of their 100-point scoring metric for code violations. In contrast, only 5 percent of the city’s fixed-location eateries failed to achieve that mark.

While the study was confined to Los Angeles, the factors that contributed to the food trucks' failing grade could be found in any city. In many cases, the tight working areas increased risk for cross-contamination of ingredients; some vendors handled money as well as food; storage temperatures can also fluctuate. In one case, being exposed to outdoor elements resulted in rodent infestation.

While they present a less forgiving preparation area, trucks aren't the only source of potential illness. In New York, up to 15 percent of stationary restaurants fail to earn an A. In Boston, 1350 of the area’s 3000 restaurants were found to have at least two infractions that could lead to food-borne illness in 2014.

If you opt for a bite outdoors, check to see if your area mandates vendors post their grades for public view, or if your county keeps a searchable list of inspected vendors online, like this one for Allegheny County in Pennsylvania. Since some health departments are only able to check portable kitchens during pre-scheduled times owing to the difficulty of locating them on a route [PDF], inquire whether inspectors have been able to witness food preparation unannounced.

[h/t Los Angeles Times]