In the 80 years since Lake Shore Drive was established as Chicago's lakeside highway, planners have struggled to strike a balance between keeping traffic moving and preserving the city's premier parkland.

The scenic avenue has undergone numerous extensions and pedestrian access projects over the years as the city has tried to maintain the historic parks and venues along the route.

On Wednesday, state and local officials revealed the most significant redevelopment plans in decades for North Lake Shore Drive between Grand and Hollywood avenues a stretch beset with traffic bottlenecks, pedestrian and cyclist overcrowding, and flooding from Lake Michigan. In the concepts, Oak Street and North Avenue beaches would be shifted, parkland added, and bike and pedestrian lanes further separated.

The big issue is the variety of users, said Jeff Sriver, director of transportation planning and programming for the city's Department of Transportation.

"It's not just a road or a highway," he said. "As many transit passengers take it as take CTA rail lines, with 70,000 riders using the corridor on buses. It's also the Lakefront Trail. Then, there's all the park activity. It's much more complex and interesting than your standard road project."

At a public meeting at DePaul University's student center, members of the multiagency task force displayed renderings and exhibits of options, which are still in the brainstorming stage.

Among those options was a proposal to add a few hundred feet of lakefill on the Near North Side, lessening the need to close parts of the road during storms.

"The extension of the park and seawall into the lake is needed to protect Lake Shore Drive from flooding, so waves will never overtop it and get into it like they do today," Sriver said. "As a happy coincidence we can use all this space as park."

The added space would allow for construction of a lane of traffic in both directions. And it would allow the notoriously sharp "S-curve" near Oak Street, where crashes and spinouts frequently occur, to be somewhat straightened. The speed limit on the curve could be 40 mph, as it is elsewhere in the road, instead of the current 25 mph in that stretch, Sriver said.

The Chicago Avenue intersection, where turning vehicles must make tight maneuvers, was reimagined without traffic signals, with Lake Shore Drive running underneath Chicago Avenue.

Officials hope the two fixes would alleviate some of the most chronically congested and crash-prone areas, which contributed to an average of 1,165 vehicle accidents a year between 2007 and 2011, according to data.

"I'm pleased with our beautiful cityscape, and they already identified safety as the No. 1 concern," said Larry Nutson, 74, of Lakeview. "But speeding and speeding enforcement is a problem, specifically in my ward with high-performance motorcycles. So, I'm hoping to see a calming of the traffic. The city needs to find a way to enforce this ... because a lot of them don't even know what the speed limit is."

The task force is also weighing reserving lanes of traffic for buses, high-occupancy vehicles or express toll lanes.

However, the congestion and safety concerns don't pertain only to drivers.

Officials presented options to alleviate run-ins between cyclists and pedestrians. In many cases, they are suggesting bicycle paths that fly over pedestrian tunnels.

While plans to separate bike and pedestrian paths along the lakefront are already underway, the new concepts seek to maintain and expand the space between high- and low-speed pathways.

Some alternatives called for the removal of a few pedestrian access tunnels and bridges, half of which are in poor condition, and the creation of new ones.

In a couple of plans, the Division Street tunnel would be removed in favor of one at Banks Street, which concerned Gold Coast resident Doug Saleeby, 62.

"I actually live near there, and I see a million kids a day ride the Red Line to go to the beach," Saleeby said. "And I don't think people who live near there would want them wandering down Astor and Banks to get there."

Wednesday's meeting also revealed options that didn't make the cut, including a suggestion for a light rail line, which the task force determined would cost $4 billion. Proposals for an underwater tunnel in Lake Michigan, an underground tunnel along Lake Shore Drive and a causeway over the lake between Chicago Avenue and Diversey Parkway were also dismissed.

At $3 billion, the tunnels would cost much more than the other alternatives, officials said, and would require hefty operating expenses for extensive ventilation systems to purge auto exhaust and smoke from traffic emergencies.

Costs and funding sources haven't been considered as of yet, according to state and local transportation officials. Projects wouldn't begin until 2019 at the earliest.

"It's really redefining the way the drive works for the future," Sriver said. "It will be the 'new drive' not the drive we got for 80 years. We want to maintain and carry forward the good aspects but also consider the function and need for the users of the park. We see a great opportunity to re-envision how it works."

tbriscoe@chicagotribune.com

Twitter @_tonybriscoe

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Lake Shore Drive proposals would shift beaches, straighten Oak Street curve - Chicago Tribune