The drive-through remains critical to McDonald's success, so it's smart it's finally paying attention to window's dysfunctional performance.

With around two-thirds of McDonald's (NYSE:MCD) revenues a direct result of the drive-through window, it's unquestionably critical for the fast-food joint to ensure the process flows smoothly. Too slow or too many incorrect orders will hurt sales.

Last year, QSR Magazine conducted a performance review of the drive-through windows at seven different burger chains. Where Wendy's (NASDAQ:WEN) got its customers through in a zippy 133.6 seconds, or a little over two minutes, Burger King serviced its customers at the comparatively glacial pace of 198.5 seconds, or well over three minutes. McDonald's, at just under 190 seconds, was also operating at a relative snail's pace.

Order accuracy was another matter. McDonald's got the orders right just 88.3% of the time, but that was still better than the 87% and the 82% accuracy ratings achieved by Wendy's and Restaurant Brand International's (NYSE:QSR) Burger King, respectively. Only Chick-fil-A got customer orders correct more than nine times out of 10.

It's probably no coincidence then that McDonald's sales have been tumbling for the past two years. It may want to pin the blame for shriveling sales on customers migrating to better-burger shops such as Five Guys and Smashburger, but it's probably had more to do with poor service at its biggest money-making operation (even if it doesn't quite explain Burger King's relative better financial performance).

But McDonald's recognizes it has a problem. In Florida, it experimented with a 60-second food-order guarantee, whereby you either got your meal in a minute or less or you got a free item on your next visit. That we haven't seen the experiment roll out nationally suggests perhaps things didn't go well there.

It's also toyed with reducing the complexity of its menu to speed up drive-through time, and presumably accuracy as well. Franchisees have long complained that McDonald's overly complex menu was a drag on their profits, and while the chain has given lip service to the idea of keeping the menu simple, it's never really followed through. It's eliminated a handful of items but then added others to take their place.

Finally, though, McDonald's is tending to is base. First it introduced all-day breakfast, something customers have clamored for for years; then it started shoring up the value end of its menu, offering a two-for-$2 menu; and now it's turning its attention to the drive-through.

McDonald's drive-through menu may have changed over the years, but it's been an overly complex ordering system that's slowed down service, led to wrong orders, and caused customer dissatisfaction. Photo: Flickr/Matt McGee.

Earlier this year it began testing what it calls "ask, ask, tell" at the drive-through window.  Throughout the transaction, employees verify the order. From when the order is taken, to payment being made, and finally when the customer receives the order, employees go over the order to ensure accuracy. McDonald's admits it will slow the drive-through process down a little, but presumably a customer will prefer having it take a few seconds longer to make it through the line if it means getting his or her order correct.

Now McDonald's is rolling out the program all across the country at all company-owned stores, while franchisees -- who operate around 90% of McDonald's domestic restaurants -- can voluntarily opt in.  

These are the types of changes McDonald's needs to make if it wants to continue growing sales. The burger chain recently reported third-quarter results showing the first period of higher comparable sales in two years, though it had nothing to do with its menu or drive-through changes. But by taking caring of the things its core customers care about, McDonald's stands a good chance of putting in repeat performances in the quarters ahead.

There remain pitfalls, of course. The ask, ask, tell policy covers only a tiny percentage of McDonald's restaurants and won't make much of a difference until it's taken up by most or all of its franchisees. It was also arguably a mistake for McDonald's to eliminate the well-known Dollar Menu in favor of the inferior McPick 2. And CEO Steve Easterbrook is not giving up his pursuit of millennial customers in his drive to change the fast-food joint into a "modern, progressive burger company."

Still these are important changes McDonald's is making, and by pursuing this path, this continues to be the best shot it has on regaining its former sales growth momentum.

Rich Duprey has no position in any stocks mentioned. The Motley Fool has no position in any of the stocks mentioned. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.