The boom in new hotel construction outside peninsular Charleston is setting off alarm bells for city planners.

At least 20 new lodgings are under construction or approved in West Ashley, Mount Pleasant and North Charleston, according to the planning departments of the various municipalities. At least four in West Ashley, 10 in Mount Pleasant and six in North Charleston are moving forward. Eight are under construction, and the others have been approved, with most undergoing plan reviews.

The suburban surge is, in part, tied to Charleston being billed as one of the world’s top tourist destinations. But some wonder how the city is going to handle all the extra traffic.

“As Mount Pleasant, West Ashley and North Charleston continue to add hotel rooms to regional inventory, Charleston’s historic Peninsula will continue to bear the brunt of this growing tourism load,” according to the 2016 Peninsula Hotel Study, which was released in June. “Hotel visitors add to traffic congestion by driving cars into downtown.”

The study makes several suggestions to handle the extra visitors.

Require all hotels in the city limits outside the downtown core to provide shuttle service for visitors and guests.

Have the city designate places to pick up and drop off visitors coming from hotels outside the peninsula.

Ask the municipalities and Charleston County to implement shuttle systems to reduce traffic and parking congestion.

The study also recommends that the city of Charleston “take the lead in initiating a countywide study of the entire accommodations industry and that such a study provide the basis for crafting a strategic regional tourism plan.”

A couple of hotels near the airport in North Charleston already provide shuttle service to the heart of the region’s tourism industry. CARTA runs hourly buses from the airport to the Charleston Visitors Center, stopping at the North Charleston Visitors Center near Tanger Outlets on the way.

“We’re likely going to do some rebranding around this route in the near future,” according to CARTA spokesman Dan Brock. “System leaders are very big on its potential. These and all CARTA services could be enhanced and expanded with increased resources.”

Charleston County’s proposed half-cent sales-tax increase, which is up for a vote in November, would bolster bus service between Summerville and downtown Charleston.

Conde Nast Traveler has named Charleston the No. 1 tourist destination in the country for the last five years in a row. Travel + Leisure recently named Charleston the No. 1 city in the world.

Partly as a result of the publicity, the number of visitors swelled from 4.22 million in 2010 to 5.15 million in 2015, a 22 percent jump, according to the College of Charleston Office of Tourism Analysis. The room supply rose just 7 percent in those five years — to 15,970 from 14,912.

But that new supply didn’t seem to put a dent in demand. Over that same period, occupancy climbed to 73.5 percent from 68.47 percent.

Thus, the boom in hotel construction, both on and off the peninsula. The city study identified five more hotels under construction and another 11 approved on the peninsula.

The tourist-fueled building boom in downtown Charleston is raising concerns not only about the extra traffic but also about the possible loss of office space and housing. This week, City Council and the Planning Commission will consider an ordinance that would forbid any hotels from displacing office space or residences. It strengthens an existing ordinance that says new hotels must not “adversely affect” the housing stock.

It’s likely not all the new hotels that have been approved will be built, and not all the visitors at the suburban lodgings will drive into downtown Charleston, according to Duane Parrish, director of the S.C. Department of Parks, Recreation and Tourism and past president of the Charleston Hospitality Association.

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But leaders are right to be concerned, he said.

“There are some that will just never get built, for a variety of reasons, and some will take a long time to get built,” Parrish said. “What’s driving this is the Charleston area has an occupancy of roughly 80 percent. The rest of the state as a whole occupancy is about 65 percent. So for a hotel developer looking to expand their inventory, Charleston is a hot market.”

Leisure travelers are driving much of the room demand but not all, he added. Part of the reason so many hotels are being built in North Charleston is because it’s a strong market for business travelers.

“Most of the hotels in the North Charleston area cater more toward the convention and corporate crowd,” Parrish said. “Those companies are generating a lot of overnight business in the north area that may never come downtown. When you take the area as a whole, it’s about 40 to 45 percent corporate traffic, which is one of the appealing things for a hotel developer here, because there’s a mix of leisure and corporate business, which is year-round.”

While it’s true that many of those visitors won’t drive downtown, planners need to be concerned about the traffic impact, he said. “The peninsula is the goose that lays the golden egg,” he said. “It’s certainly one of the biggest draws. There are a significant number of people who want to see that and come downtown.”

Public transportation will have to be bolstered to handle the extra visitors, he said.

“Charleston has been discovered and rightly so,” he said. “People want to see it and enjoy it. From a long-term standpoint, there needs to be planning in place for infrastructure well beyond the peninsula. Moving people around without a car is the key long-term to making all this work.”

Reach Dave Munday at 843-937-5553.