The War Memorial estimated about 120,000 people attended the Dawn Service, 80,000 more than last year and more than double the 50,000 authorities had been expecting.

Angry passengers took to social media to express their disappointment with the service, which stopped some people from being able to get to the dawn service at the Australian War Memorial.

"I travelled from Orange to attend the dawn service but unable to get there [because] there were over 400 people at the Woden bus terminal," one woman wrote.

"Then went into Civic to be told that there would only be one bus for over 150 people, so went back to accommodation and watched it on TV. Very, very disappointed."

However, another replied defending the bus service.

"I am sad you didn't get to attend but i think the bus service did very well. They were expecting 50,000 people not 120,000. To cope with that extra capacity was hard work but they did it. After laying a poppy at the war memorial we walked and caught a bus almost immediately. Well done to ACTION buses," she said.

Another Canberran said thousands of people had been left standing in Woden due to the lack of buses.

A Monash resident said he had gone to the Tuggeranong bus interchange at 4.15am to catch a bus to the service, as he did most years, only to find thousands waiting in the cold.

"There would have been a line of people standing three a breast, 300 yards long, on platform 9 - perhaps 1000 people," he said.

"I noticed there was no ACTION bus supervisor. Two articulated buses departed, leaving about 700 people behind."

The resident said it took until 5.10am to try and get a bus before going home, at which point there were still people waiting to get to the dawn service.

"It doesn't require a genius to work out that the 100 year centenary of Anzac would require extra bus services ... I like many am very disappointed that we could not attend the service," he said.

A spokesman for the Territory and Municipal Services Directorate said a necessary change to temporary traffic measures by police part way through the morning meant buses were unable to return to interchanges as quickly as expected.

"While more people attending the service than originally forecast, in addition to associated traffic, did affect bus running times, ACTION was successful in transporting over 20,000 passengers to the service from all over Canberra," he said.

"ACTION staff report that bus interchanges were mostly clear of people wanting to attend the service by 5:20am."