"The beauty of Detroit … is that second-tier cities are attractive because you can get the room blocks, and in many cases, avoid busing" attendees from hotels in outlying areas, said John Graham IV, president and CEO of the Washington, D.C.-based American Society of Association Executives.

ASAE brought its annual conference and 5,300 meeting planners and association executives to Detroit in August 2015 for the first time in its 95-year history.

Though Cobo Center can accommodate larger groups, conferences with larger numbers of attendees, in the range of 5,000-7,000, are often forced to book rooms in the suburbs.

"When you have to start to go out to Dearborn to get people to the convention center, it gets less and less attractive," Graham said.

The city has done a very good job of positioning with sports teams, the coming of light rail and the development of areas like New Center, which is quite a change from 2009, when ASAE booked the conference, Graham said.

"… People asked, 'What the hell were you thinking?' " Graham said.

"Now people have been there, have seen it and have come to say it's becoming a vibrant, welcoming city with a great waterfront, a great convention center and a renewed automotive (industry)."

Detroit is riding a rising tide, but to truly compete, it still needs more hotel rooms in the central business district within walking distance to Cobo or a five- to 10-minute taxi ride, Graham said.

It's a thought the Detroit Metro Convention & Visitors Bureau has been echoing for years.

Cobo Center's renovations and the city's comeback are giving meeting planners a reason to look at Detroit, said Michael O'Callaghan, executive vice president and COO of the visitors bureau."But the one area we are lacking is in the number of available rooms in the convention district."

The opening of the Aloft Detroit in the historic David Whitney Building brought 136 rooms in December 2014, and the Foundation Hotel in the historic firehouse across from Cobo is expected to provide an additional 100 rooms when it opens in the spring.

The Foundation Hotel is one six hotel projects in development that could bring roughly 970 more rooms to the downtown market over the next few years. Since then, contemporary furniture retailer West Elm announced its plans for a boutique hotel with more than 135 rooms and a retail store on Cass Avenue in Midtown, which brings the total number of hotel rooms in development or planned to 1,105 through multiple boutique projects.

Additionally, the Crowne Plaza Downtown Detroit Riverfront is considering a plan to build another tower, which could bring another 400 rooms online.

The boutiques are nice, but adding that second tower to the Crowne Plaza or developing another 500- to 700-room hotel downtown would give the city more room blocks and make it even more competitive, Graham said.

Occupancy, average daily rates and revenue per available guest room point to rising demand for hotel rooms in the downtown area.

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Occupancy for Detroit's downtown hotel rooms was 68.2 percent in 2016, up from 65 percent the year before, O'Callaghan said. The average daily rate was $151.63 last year vs. $147.01 in 2015, and revenue per available guest room was $103.41 versus $95.60.

With the hotel rooms downtown running at higher occupancy levels, it's likely to become tougher for hotels to reserve large blocks of rooms for groups, he said.

A balance is needed to sustain a larger number of hotel rooms, but the prevailing thought is that if the hotels are built, the conferences will come.

Experts told Crain's last September that the market demand could support 800 to 1,000 more rooms downtown in the next two to three years.

But beyond that, hospitality expert Ron Wilson, CEO of Troy-based Hotel Investment Services Inc., cautioned against adding additional rooms to the downtown market until more conventions or other demand materializes to absorb the new supply.

In addition to the number of hotel rooms downtown, the airlift into Detroit and the costs of hotel rooms and food, planners are scrutinizing convention center offerings, Graham said.

Cobo's recent renovation and expansion is in keeping with updates happening at many other convention centers around the country, he said.

"I remember the days when you walked in and faced a cement wall facing the river," he said.

Following the $279 million renovation and expansion project, which wrapped up in August 2015, Cobo's views, layout and amenities are excellent, Graham said.

Today, visitors can see views of Canada and the Detroit RiverWalk from the 30,000-square-foot, glass-walled atrium and access the Detroit RiverWalk directly across from it.

Among other things, the upgrades, which added about 30,000 square feet, increased parking and improved traffic flow, upgraded infrastructure, enclosed loading docks and redeveloped the former Cobo Arena as a 40,000-square-foot grand ballroom.