Four years ago, thousands of ticket-holders hoping to see the inauguration of the nation’s first African American president failed to get there, shut out of their spots on the U.S. Capitol’s lawn because of security and crowd-control problems.

They included several hundred people with purple-coded tickets who became stuck for hours in the Third Street tunnel, which later became known as the “Purple Tunnel of Doom.” Throughout their long, fruitless wait, they laughed, cried, shivered and, at one point, sang an impromptu chorus of “Lean on Me” — footage that remains on YouTube.

Inauguration officials said they are doing everything they can to ensure that there will not be a similar ticket fiasco for President Obama’s second swearing-in.

This month, they announced that the Third Street tunnel will be closed. They will also be increasing the number of signs directing ticket-holders, adding more civilian volunteers as guides, bringing in backup generators for security checkpoints and establishing a social-media hub where law enforcement agencies can monitor Twitter and other sites for problems as they play out in real time.

“We’re committed to fixing what went wrong to make sure everyone who had a ticket gets to their place on time,” said Sen. Charles E. Schumer (D-N.Y.), chairman of the Joint Congressional Committee on Inaugural Ceremonies, which oversees the day’s events at the Capitol.

Military and National Guard officials held a press conference to detail some of the 2013 Inauguration plans at the Armory in D.C., using a 40 by 60 foot map of the National Mall and its surrounding areas to plan logistics and staging. (AJ Chavar/The Washington Post)

Overall, officials have said they expect the crowd for the Jan. 21 ceremony to be much smaller than the 1.8 million who attended last time — perhaps closer to 1 million. But Schumer’s committee will be distributing a similar number of tickets for standing and seated spots on the Capitol lawn, about 250,000, which are given to lawmakers to distribute to constituents. Last time, about 241,000 tickets were distributed with color codes for various entry points — orange, yellow, blue, silver and purple. At the time, they said 5,000 were shut out, but the number was probably higher.

They’ll use the color-coded system again — but no purple tickets.

Schumer said the committee has created a wide-ranging signage system that will direct the flow of people beginning at Metro stations and major landmarks to their ticket gates and send those without tickets to the general assembly area on the Mall, where the inauguration ceremony will be broadcast on large screens. There will be three to four times the signage in January compared with 2009, when there were about 30 banners and message boards.

In other measures, the committee and law enforcement are adding generators. Last time, one of the power sources failed in the cold, adding to the chaos. There will also be more magnetometers — metal detectors — at security checkpoints, about 160 in all.

“Although we cannot discuss the means, methods, specific resources, or numbers we utilize to carry out our protective responsibilities, we can say there is a tremendous amount of advance planning and coordination,” Secret Service spokesman Brian Leary said in a statement. Agents have been undergoing a variety of training initiatives to prepare, including medical emergencies, scenario exercises and field exercises, Leary said.

Representatives from various law enforcement agencies will gather at a hub to monitor Twitter and other social media. Last time, law enforcement did not see several desperate tweets from those stuck in the Third Street tunnel.

A 2009 report conducted by the Secret Service and other law enforcement agencies for the congressional committee determined that “flaws and shortcomings in the planning process” caused the chaotic atmosphere at the last inauguration, as did insufficient signage, poor coordination among law enforcement agencies and a lack of personnel to provide information to visitors.

U.S. Capitol Police had 350 “way-finders” in place four years ago. This time, they will use “significantly more” volunteers — wearing brightly colored jackets — to guide the public to the appropriate gates, officials said.

In the early hours of Jan. 20, 2009, thousands of people made their way to the Capitol grounds, flooding streets and quickly jamming entrance gates. They waited hours in line as security personnel struggled to move them through an insufficient number of magnetometers.

As the cold morning wore on, tempers flared. At one point, a group of those with silver tickets trampled a storm fence near the Ulysses S. Grant Memorial, causing further delays when Capitol Police sent in “civil disturbance platoons” to quell the disruption, the report said.

And thousands ended up stuck in an impromptu line inside the Third Street tunnel, which they thought was an access point to the gate for purple tickets.

“It was freezing, and there were icicles falling from different parts of the tunnel. I couldn’t believe how logistically unsafe it was,” said Jack Weingart, 24, who was then an American University student and is now a staffer at “60 Minutes.”

Weingart and others tried tweeting their predicament — “Purple ticket holders in line — at least a mile long . . . Right now waiting in a tunnel, iv e been here since 7,” Weingart wrote — but no one came to their aid. When Weingart finally emerged from the depths, he found the entrance gate closed and ended up sitting on the a nearby sidewalk, where he listened to the president’s speech on someone’s boombox.

“I missed it all,” he said. “It was just a blur.”

Outrage quickly spread throughout the city. Foreign Policy blogger Marc Lynch, a George Washington University professor, posted about his ill-fated hours in the underpass and dubbed it “the Purple Tunnel of Doom.” The nickname caught on with others who were with him, inspiring a Facebook page that ultimately had 6,000 members. They even designed their own T-shirts.

Lynch said he’s “quite recovered” from the experience but doesn’t know what he’ll be doing for the next inauguration.

“I do hope that they are better organized this time,” he wrote in an e-mail. “All joking aside, it wasn’t just that we missed the inauguration, it was deeply unsafe in that tunnel, and if people had realized we weren’t getting in there could easily have been a stampede. Plus, no bathrooms.”

As for Weingart, he eventually got back to campus but vowed that it would be the last inauguration ceremony he would ever try to attend.

“I think the best seat in the house was from your home,” he said. “I’ll keep to the living room and the couch.”