London Underground: What ‘fast’ and ‘semi-fast’ mean on the Metropolitan line and why we have them

The world’s oldest underground line has always been something to marvel at, whether it was thanks to its innovative construction methods, its massive expanse from city to countryside or creating the entire Metroland development which has made North West London what it is today.

Its timetable is something rather curious too. As the only London Underground line to formally publish a public-facing timetable for all trains, its complexity might seem daunting but is all aimed to balanced the unique needs of passengers at each ends of this very unusual route.

In the city, the line shares tracks with two other lines, in the suburbs the line acts as an express service semi-duplicating a different line and beyond the city limits the line becomes a sort of part-commuter part-branch line railway.

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As such, every weekday peak hour period and occasionally at other times, trains are split into three service patterns: fast, semi-fast and all stations.

This is what each of those means and how you can make sure you get to your destination as quickly as possible:

Fast trains

Fast and semi-fast trains run on tracks which do not have platforms at smaller stations served only by all stations trains such as here at Northwick Park

Fast Metropolitan line trains run between Amersham or Chesham and Aldgate.

On weekday mornings (6-10am), they run from Amersham or Chesham to Aldgate and on weekday evenings (4-8pm) they run from Aldgate to Amersham or Chesham. Occasionally they can operate at other times.

Fast trains call at all stations between Amersham or Chesham and Moor Park, then run fast to Harrow-on-the-Hill, then fast again to Finchley Road and then all stations to Aldgate. In the evenings, fast trains to Amersham or Chesham also stop at Wembley Park.

A fast train is only four and a half minutes faster than a semi-fast train or seven minutes faster than an all stations train between Moor Park and Finchley Road meaning it is usually faster to catch a slower train unless a fast train is due in the next seven minutes.

Fast trains cannot run to Uxbridge and usually cannot run to Watford due to the way the tracks are configured.

Fast trains usually use a different set of tracks between just south of Wembley Park and just south of Rickmansworth which allow them to run past intermediate stations non-stop at speed however fast trains can occasionally run non-stop on the lines used by all stations trains at reduced speeds.

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Fast trains are not to be confused with Chiltern Railways services which provide the quickest journey times between London, Harrow-on-the-Hill, Rickmansworth, Chorleywood, Chalfont & Latimer and Amersham.

These are National Rail services, and while you can use contactless and Oyster on them just like the Metropolitan line, they run at different times, different rules apply on them and they are not operated by Transport for London (TfL).

A Chiltern Railways train is nine minutes (seven if it also stops at Rickmansworth) faster than a fast train between Central London and Chorleywood, 12 faster than a semi-fast train and 15 minutes faster than an all stations train.

As Chiltern trains run less frequently than Met trains, it’s again usually quicker to take a slower one.

Semi-fast trains

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Semi-fast trains like this one usually run between 6am and 10am plus between 4pm and 8pm on weekdays

Semi-fast trains call at all stations except Wembley Park, Preston Road and Northwick Park. They can run to any destination but usually run between Baker Street and Uxbridge or Watford.

Just like fast trains, in the evenings semi-fast trains to Amersham, Chesham, Uxbridge or Watford also stop at Wembley Park.

A semi-fast train is only two and a half minutes faster than an all stations train meaning that unless a semi-fast train is right behind an all stations train, it’s usually quicker to take the all stations train.

All stations

This one is self-explanatory, these trains run to all Metropolitan line destinations calling at all of the stations en route.

There are a handful of Metropolitan line services each day which only run between Watford or Rickmansworth and Chesham or Amersham which do not have a service pattern description.

These trains are all stations trains. On weekends, all trains are scheduled to be all stations.

Trains can also run on a so-called secret part of the Metropolitan line which takes trains between Rickmansworth and Watford called the Croxley North Curve.

This part of the line is not shown on the Tube map as it is only used by around three trains per day, hence why it’s often referred to as ‘secret’.

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At the discretion of the line controller, when the service is disrupted the destination and the service pattern of a Met train can change at any random point in the journey.

An all stations train from Baker Street to Watford can become a fast train to Chesham at Finchley Road for example if the controller decides this is the best way to provide the best service to the greatest amount of passengers on the line.

For this reason, the Metropolitan line is full of signs which advise passengers that if no through train is shown to their destination, they should take the first train and change where necessary.

Do you travel on ‘fast’ or ‘semi-fast’ Metropolitan line trains? What do you make of the service? Tell us in the comments below!

You can read all of MyLondon’s Tube-related news stories, features and trivia pieces on our dedicated page here.

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