More than half of the U.S. population aged 18-64 (53%) have shopped in a store and been in a car during the same half-hour in a given week, according to data exclusively provided to Inside Radio by cross-platform measurement service USA TouchPoints. “Whether that’s coming home from or going to the store, there is a direct adjacency there,” says Matt Hird, senior research analyst, USA TouchPoints.

And among consumers en route to and from shopping, AM/FM radio accounted for more than three-fourths of their share of audio time in the car. Broadcast radio (77.4%) topped all other audio sources, including satellite radio (14.3%), CD, record or tape player (4.1%), iPod/MP3 player (3.9%) and streaming audio (1.4%). “AM/FM remains ideally suited for in-car audio while people are going about their daily lives and making their shopping decisions,” says USA TouchPoints director of global research Paul Street.

Pierre Bouvard, Cumulus Media and Westwood One chief insights officer, says this new data demonstrates radio’s proximity to consumers as they’re getting ready to swipe their credit card or plunk down their cash. “We are the soundtrack of America’s shopping trips,” Bouvard says. “This is the perfect medium to reach people when they are in the shopping mindset and thinking about what brands they want to buy.”

The new data reinforces a separate Starcom Mediavest Group study conducted by USA TouchPoints parent RealityMine that found radio and out-of-home media influence purchase decisions the most. The Starcom study uncovered a 0.91 correlation between audio ads and purchase activity. That’s considered to be a very high correlation—the closer you get to one, the higher the correlation between purchase and media exposure.

Pulling the camera back to a wider angle shot off all times Americans spend in a car, not just en route to shopping, USA TouchPoints found the vast majority of audio consumed is through AM/FM. In fact, 40.7% of the time that someone is in a vehicle, they’re listening to some sort of conventional radio, either terrestrial (34.6%) or satellite (6.2%).

Importantly, the new data uncovers a key window of opportunity radio offers marketers to influence consumers as they’re in their cars going about their busy lives. Fast food purchases, for example, are 57% more likely to be considered in the same half-hour as car travel than they are in daily life. “There is no more perfect ad medium for fast food than AM/FM,” Bouvard says. “You’ve got me in the car, I don’t have a refrigerator in the back seat, I’m hungry, and I’m sitting in something that can take me to the actual place that will feed me the burger and fries.”

Fast food isn’t the only product purchase more likely to be considered within 30 minutes of car travel. In fact, the restaurant and bar category has a major in-car opportunity to influence consumers. “Of all the hours in a week that somebody is considering a purchase at a restaurant or a bar, they are 49% more likely to be in a car vs. the rest of the week while they are considering that purchase,” Hird says. These numbers reflect all travel in the car and not just en route to or from shopping.

USA TouchPoints is able to calculate these purchase and consideration metrics by virtue of its methodology. In addition to passive measurement, the service uses an e-diary wherein survey panelists enter their media usage, along with other information, every 30 minutes.

The data shows consideration frequently translates into purchase. Fast food is 72% more likely to be purchased in the same half-hour as car travel, health/pharmacy products are 43% more likely to be purchased, groceries (33%), house and garden (12%) and pet related goods (5%).