But last night was different. Just over an hour into the journey, a frantic sounding of the train's siren was the signal that something was wrong. Those reading their papers looked up; those dozing shook themselves into life. Then, in an instant, their world was turned upside down.
Barry Keates, 61, a semi-retired City worker from Hemel Hempstead, said: "I was sitting trying to do the crossword which I usually do when suddenly I realised that there was trouble at the last minute, because the driver started to sound his horn and he sounded it increasingly.
"Then we were braking and there was a tremendous bang. I was right at the front of the train and I think there were three other people in there. The carriage tipped on to its right-hand side and we were thrown about in all directions. It was like being a pea in a concrete mixer."
Mr Keates suffered a broken arm and a cut to the side of his head; he said another passenger was much more badly injured.
"We couldn't do anything for him. Before long, a fireman came through the top and started to help the guy. Then they started to get us up a ladder through the window."
One woman passenger was killed and more than 60 passengers were injured. Four of the casualties had serious injuries, a police spokesman told a news conference in Watford. A pregnant woman was hurt and the driver of one of the trains was treated for multiple injuries.
Up to 40 people were trapped in the wreckage when part of the commuter train, believed to be carrying 400 passengers, was derailed and tipped on to its side after it collided with an empty stock train coming from Bletchley to Euston. Overhead power lines were brought down in the crash.
The engine and the front carriage of the commuter train, a four-coach electrical unit, ended up on top of the stock train. Carriages were splayed both ways from the head-on impact.
Mel Carrie, 25, a learning resources officer, whose home overlooks the scene, said: "It was horrendous, like thunder. It wasn't a bomb-like blast, it was the sound of a collision."
Roger Taber, 48, a television journalist who was working nearby, heard the train siren a moment before the impact. "There was a terrific crash and then a lull. And then gradually came the sirens of the emergency services until it became a cacophony of sound," he said.
He described the rescuers as "incredible. To see 10 people gently easing a stretcher down an embankment so professionally was an amazing thing to watch. They were here almost immediately. Then the air ambulances came - some of them landing incredibly close to the wreckage."
The injured were ferried to Watford General Hospital, where the manager, Mike Kerrigan, said 62 casualties were being dealt with - nearly half of them women. Four were seriously hurt and seven had less-serious injuries, including broken arms, legs and ribs.
Howard Borkett-Jones, a consultant in the accident and emergencies department at Watford General, said: "Most patients had minor cuts and injuries, and we have had 11 who have required admission.
"A number of people have serious fractures but no one is critically ill at the present time," he said. A train driver was one of those detained.
"A lot of the people here had injuries consistent with injuries from glass, and being thrown against the internal structures of railway carriages.
"It is what we expect from a train crash - a large number of patients with large numbers of cuts and bruises and [others] with more serious injuries."
Last night, as dusk fell, fire-fighters scrambled inside the twisted wreckage to fix lines to an overturned carriage that threatened to roll down an embankment on to houses below.
The front carriage of the empty train had risen at a grotesque angle and was resting in the air.
A Railtrack spokesman said: "A full investigation is already under way. We will be checking all the equipment involved - signalling, the condition of the track, all the hardware - and taking statements."
The investigation would be led by Railtrack's Midland Zone. For the time being the track, which forms a stretch of the West Coast mainline, remains completely blocked. The spokesman could not say whether it would be possible to clear the line and reopen access into London's Euston by tomorrow's rush hour.
The investigation into the crash will include a key role for Her Majesty's Railway Inspectorate, part of the Health and Safety Executive.
Vick Coleman, HM Deputy Chief Inspecting Officer of Railways, said last night: "We will conduct a thorough and independent investigation into this accident and will ensure that the cause, or causes, are determined so that decisions can be made on ways to prevent any recurrence.
"We will also consider whether there have been any breaches of relevant law. It is too early to speculate on the outcome of our investigation."
Sir George Young, the Secretary of State for Transport, expressed his "deepest sympathies" for the dead and injured and praised the emergency services for their efforts.Reuse content