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Chipotle says it is addressing a top customer complaint by making ordering much faster and more efficient.

"The number one complaint that customers have is long lines," Chipotle Chief Marketing Officer Mark Crumpacker told analysts on Monday.

Chipotle executives have conceded that service is getting slower, and said they are trying to speed things up by retraining employees and getting better at predicting demand.

Chipotle is also experimenting with new ordering systems, such as tablets and "virtual drive-thrus" that will enable customers to skip long lines and potentially avoid coming inside the restaurants altogether, Chipotle CEO Steve Ells said.

To manage demand from tablets and online orders, Chipotle's restaurants have started adding what the company calls a second "make-line," or team of workers that prepares virtual orders from a prep table in the kitchen. The second line is located in the kitchen to avoid bogging down the main, customer-facing preparation line.

"This new make-line will enable digital orders to be made more quickly, accurately, and efficiently, and it will allow for tablet ordering as a way to skip the queue and eventually for things like virtual drive-thrus or other ways to order outside the restaurants," Ells said.

Ells didn't explain what he meant by a virtual drive-thru. Chipotle spokesman Chris Arnold declined to expand on the concept. Other restaurants have used that term to describe curb-side pickup services.

If Chipotle implemented curb-side pickup, customers would be able to order Chipotle online and then pick up their food without ever leaving their cars.

That would be a game-changer for Chipotle, which is one of the only fast-food restaurants that has refused to embrace drive-thru lanes.

Ells also provided an update Monday on online ordering, saying the company has improved the lag time between when orders are placed and when they can be picked up at restaurants.

Through a new "smarter pickup" technology, the company has "dramatically shortened the wait time after a digital order is placed," he said.

The smarter pickup technology will be rolled out nationwide by January. It sets a lag time for online orders automatically based on each individual restaurant's level of demand at any given time. Previously, restaurants were able to set that lag time, and many customers claimed that their wait for online orders would be 30 minutes or longer.

By comparison, Starbucks mobile orders during peak morning periods are typically ready three to seven minutes after ordering, and Chick-fil-A prepares mobile orders immediately, as soon as customers arrive at the restaurant.