Taco Bell debuted fries for the first time in late January.

Traffic spiked 38% the day after the nacho fries launched, according to new data.

Fast-food chains including Taco Bell and McDonald's kicked off 2018 with a battle for bargain-shopping customers.

Taco Bell's fries are already bringing more customers to the chain.

In late January, Taco Bell added $1 nacho fries to the menu for a limited time. Instead of taking the classic fast-food route, Taco Bell tops its fries with a spicy seasoning and serves them with a side of nacho cheese.

Foot traffic spiked by 38% over average the day after Taco Bell launched its new fries, according to inMarket location data. And, the increase appears to have continued over the next week, with traffic remaining above average throughout the rest of January.

InMarket uses mobile device data to track customer visits at major US restaurants and retailers, analyzing patterns from 50 million monthly users.

The new fries "are the perfect example of Taco Bell's belief that you shouldn't apologize for value, but celebrate it," Yum Brands CEO Greg Creed said in a call with investors on Thursday.

In advertising, Taco Bell took aim at McDonald's and other burger chains' spicier seasoned fries, served with nacho cheese, as vastly different than the typical fast-food fare. Taco Bell also took some jabs at McDonald's for serving fries that cost more than $1 — despite the chain's recent introduction of a new value menu.

Early 2018 was packed with fast-food chains trying to one-up each other to win over budget-conscious shoppers.

In early January, McDonald's debuted the "$1 $2 $3 menu" — a new take on its iconic Dollar Menu. Subway launched a revamped $5 footlong deal, with five sandwiches priced at $4.99. And, Wendy's expanded its 4 for $4 bundle deal.

Taco Bell announced in December it's expanding its dollar menu. The nacho fries were the first of the 20 $1 limited-time offerings that Taco Bell plans to roll out throughout 2018.