The excellent Human Transit blog reports that London’s Circle Line is being turned into something that more represents a “tadpole” – well at least according to Jarret from Human Transit.
The difference between the old line and the new are clearly visible in the two maps below. Firstly, the old (current) map:
And now the new one:
The obvious question I had was “why the change?” Circle lines seem very effective – that you’ll always end up where you need to go eventually, and a certain security about the completeness of it. However, with the advantages of circular lines, there are also apparently some pretty significant disadvantages. Human Transit explains how these disadvantages have led to the changes in the operation of London’s Circle Line:
Why did the Circle Line come apart? Because it was hard to operate reliably. Reliability depends on regular breaks that give a late service the opportunity to catch up to its schedule. Human drivers obviously need breaks too. Actually, the transit industry usually distinguishes between two kinds of break:
- Layover is the time a human driver needs at the end of a line, to do personal business, meditate, snack, whatever.
- Recovery is spare time in the schedule whose purpose is to enable a late vehicle to get back on time.
Many labor contracts and operations policies have complex formulas governing these two things, but in broad terms, a bus or tram in mixed traffic needs at least 10% of its time to be layover and recovery, and often closer to 15%, while exclusive right-of-way services may need a bit less.
And since nobody wants to be waiting on the vehicle while these breaks occur, efficient transit lines have endpoints where the vehicle will be empty. Most transit lines that are presented as continuous circles have some provision for this, but it’s often awkward. On the Circle Line, drivers took their breaks by leaving the vehicle and taking over one a few minutes later, a method called “operator fallback,” which provided layover but didn’t solve the problem of recovery. Now they’ll have both, and they should see better operations, and perhaps even happier drivers.
Basically, because the service operates as a circle once it got behind its scheduled timetable there was not really any opportunity for it to recover. For services that properly “terminate”, there is time for the train/bus/tram/whatever to either wait a while before beginning its run without inconveniencing passengers (if it’s running on time) or make that time up if it’s running late. I remember the first time I caught the Circle Line there was a period where it stopped at a station for quite a few minutes, which was only slightly annoying to me (as we weren’t exactly in a hurry) but could have annoyed a regular user to a greater extent.
In terms of bringing this back to Auckland, the obvious equivalent is the Link Bus route – which in some ways suffers the problems of being a circular service even more than London’s Circle Line. This is because The Link does not run in its own right-of-way – and actually has an embarrassing lack of bus lanes along its route. As all regular users of the Link Bus know, they have a nasty habit of coming in “bunches” – long gaps with no buses and then plenty of buses coming at the same time – as well as having the annoying Victoria Park delays, where the bus waits for five or so minutes before shifting onwards (usually without the driver informing passengers annoyingly) so that its timetable can “catch up”.
I wonder whether there would be a reason to do something similar to the Link Bus route as is being done to the Circle Line – to turn it into a kind of “spiral” type service (perhaps with its new branch out to the Tank Farm area once it develops?) Or would the disadvantages of breaking up the circular route of the Link outweigh the advantages? I must say I’m skeptical about whether the changes to the Circle Line in London will make things better for the user, as it seems like they’re being made with the benefit of the operator more clearly in mind. I’m generally of the opinion that public transport should be tailored to best suit its users, not make life easier for its operators – and in fact I think that the operator based system has caused many of the problems faced by Auckland’s current system. Perhaps with the Link we just really need smart-card ticketing (to speed up boarding times) and more bus lanes (preferably along its whole route) to avoid bus bunching and enable more reliable travel times – which would reduce the need for the “Victoria Park wait”.
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Hmmm, some lessons for the “Isthmus Loop”… I think with a well written timetable and sidings there is no reason a circle loop (rail) cannot be run effectively and on schedule…
I agree on the improvements to the link…
I agree there. If the operational difficulties can be overcome I think that loop services have some advantages… and they seem to work OK in Moscow and Tokyo. I wonder if London will regret this decision, or perhaps there are other reasons for this we don’t know about.
I think the problem is much worse with buses than trains, with the longer the route the bigger the problem.
This is a well known issue with Christchurch’s otherwise successful Orbiter service, which also has a notional 10 minute timetable. Most users have a story where they were waiting 20 minutes and then two buses turn up, this really makes joke of the 10 min frequency and diminishes its value for transfer, which was a main point of it coming into being.
I think a good solution is to increase the frequency, changing to a 6min – 7min frequency would solve many of the problems. Although there is the issue of operator incentives to ensure they keep to this frequency. Hopefully the patronage increase after a few years from increased transfers would cover much of the costs of doing this.
An ithsmus loop line could work well, particularly if the layover/recovery time is sheduled at a junction of routes, such as Onehunga or Penrose. That way people can make a connection if need be to carry on their way, and only minimum of people heading though would be inconvenienced.
The trouble with the Circle Line is that disruptions to service don’t clear themselves. An incident (mechanical problem, passenger medical, what ever) that holds up a train for 20 minutes means that there will be a 20 minute gap between trains for the rest of the day with subsequent trains clustered after the delayed train.
On the other lines, it is standard practice to terminate and turn back trains before their normal destination in order to restore normal service frequencies and spacing. Making the Circle Line linear gives this opportunity. It is a good idea.
Why can you not terminate and turn back trains on a circle line in the same way? That would mean only the section of track between the two nearest crossovers either side of the blockage would be closed, turning your circle line temporarily into a C shaped line.
Why not? It’d be a very tricky thing to do on a circular line. You’d have a (say) 20 minute gap on clockwise and want to turn a couple of anti-clockwise trains around in front of the next clockwise train in order to fill the gap. That’d leave you with a clockwise/anti-clockwise imbalance. The obvious solution would be to turn around a couple of clockwise trains waiting behind the leading clockwise train. But there isn’t an obvious gap for them to slot in to. It all sounds really complicated and risky, with the potential to mess the schedule up even worse than it is. You’d also need a lot of crossovers, whereas the linear lines in London typically have them only at a few key stations.
But thats no different than if you wanted to close one direction on a linear line and keep the other going, you’d have exactly the same issues and imbalances.
There is nothing different between managing a blockage on the middle of a linear line than in the middle of a loop line, except on a loop line people have the option of taking the long way around via the remaining open section.
The problem with the Circle Line is that it shares its tracks with two other underground lines. Any interruptions on those services cause the Circle to stall too.
If I may plug an excellent blog about the London Underground (and much, much, MUCH more): http://diamondgeezer.blogspot.com/
The Link bus needs to cut out the U turn that it makes on Symonds/ Queen Street and just go straight on to Karangahape road