Shortly after 7 a.m. yesterday, three Dublin buses, almost identical to those involved in last week's crash, approached the Clarence Hotel on Wellington Quay.
Dawn had just broken over Dublin, and few people braved the cold to catch a glimpse of the Garda reconstruction.
Articulated lorries rumbled past and the odd taxi-driver slowed to take a look before the quays were sealed off. Some of Dublin City Council's cleaning staff swept the area before the reconstruction began.
Three people from Co Clare claimed to have arrived especially for the reconstruction.
Members of the Garda transport investigation team arrived, assisted by other members of the force and CIÉ engineers.
The driver of one of the buses, a uniformed Garda who wished to remain anonymous, said a number of theories were to be examined.
Yesterday's exercise was an attempt to establish the speed at which the bus was travelling when it went out of control and crashed into the stationary 66 bus, killing five people and injuring 20.
Just over a week previously, the scene had been one of chaos and horror but yesterday's was a clinical exercise attempting to shed some light on the tragedy.
The road had already been marked with yellow paint to indicate the position of the buses following the crash.
Two empty buses were manoeuvred and placed exactly as they were on the day of the incident and photographed from every stage.
Two cranes were used to allow pictures to be taken from a height.
All the information gathered yesterday will form part of the investigation file. A report is expected within a month.
So far, gardaí have interviewed more than 50 people and taken camera footage from the Clarence to help them with their investigation.
Supt Tom Conway said yesterday's reconstruction was an attempt to put together what exactly happened "to get a better picture" of the accident.
The operation was watched by independent observers from the Dublin Bus investigation team.
Reconstructions like yesterday's occurred regularly, according to gardaí, but they are rarely as high profile.
The operation started within sight of the bouquets of flowers which have been left in sympathy to the families of those who lost their lives.
It was finished at about 11.15 a.m.
The quays were reopened and the buses rolled back on to the busy roadway.
One sympathy card at the scene reads: "If only we had the words that might offer a little comfort, ease a fraction of the pain ... we could let you know that you're not alone during this tragic time. But we don't because the words simply don't exist."