Distant Oysters

Here's a fun question about London transport:

What's the farthest distance you can travel on an Oyster card? That is, the basic travel pass in London?

I thought I knew the answer - surely it's from Gatwick Airport, located in West Sussex, to Hertford North, located in (unsurprisingly) Hertfordshire. That's only twenty stops, according to Google Maps, albeit with an interchange at Finsbury Park, and is over fifty miles on foot. 

But I was wrong.

I believed it to be correct because Gatwick is the biggest extremity in the Oyster zone - for those who don't know, here's a link to a rail map that shows the Oyster zone. Logically travelling south to north between two places that aren't even in London should constitute the longest distance. The furthest station west is still in London, so any possible route should have to be:

• North to East
• North to South
• South to East

(but not necessarily - east to west can also be lengthy, as we'll discover.)

There's also the debate to be had about distance or magnitude. For example, I could walk around a roundabout 150,000,000 times and walk a greater distance than if I walk from Gatwick Airport to Hertford North, but my displacement is much, much smaller. All of a sudden, this is a mathematical question, and I'm going to use the displacement from now on.

It should be obvious Gatwick should be part of the route, so let's see all the possible distances between different points in the Oyster Zone. Specifically, distances to places at (Oyster zone) termini outside of London. I'm also excluding stations like Grays as they're going to be closer than Shenfield for obvious reasons - we're starting from Gatwick.

Gatwick to:

• Shenfield - 62.78 km
• Epping - 62.65 km
• Broxbourne - 66.42 km
• Hertford East - 71.68 km
• Hertford North - 71.54 km
• Potters Bar - 60.13 km
• Radlett - 59.75 km
• Watford Junction - 58.65 km
• Watford - 58.43 km
• Chesham - 68.45 km
• Amersham - 65.33 km
  

So I was wrong in my assumption - as often happens, the "cardinal direction paradox" has seen an eastern station be more northern.

Except Ware has a displacement of 72.98 km, so maybe that approach wasn't the best one - now Gatwick to Ware is the longest. To finish this off, I've decided to focus on journeys from east to west, preferably also north to south and vice versa. One trip, from Grays to Amersham, had a displacement of about 68 km, which would make it one of the longer possible journeys. Yet I don't think any can beat Gatwick to Ware, a trip that requires one more trip than the journey to Hertford North.

But we can take this one step further. Theoretically, we can always take buses as well if the Oyster zone is unforgiving for trains. Take the massive Crossrail branch out to Reading - untouched territory to this point. As before, we'll be using displacement. 

If you took the Elizabeth line from Shenfield to Heathrow, took any bus to the Nene Road stop, crossed the street and took the 81 bus to Slough, you'd be very miserable. However, you'd also have covered a displacement of 65 km, which isn't too bad. If we started from Ware and ended up in Dorking by taking the 465, we cover 68 km. On a sunny day, you can travel from Amersham to Winston Churchill's stately house Chartwells and cover 67.5 km. The M25, however, is only about 60km wide at given points, and buses don't travel much further than that usually. 

I'm thus happy to claim that 73km is the longest distance possible, from Gatwick Airport to Ware, a journey I reckon very few people do annually. The best part is that Ware isn't even a terminus, and the trip takes less than two hours to complete. That said, there are far better things to do than do this for fun. Indeed, I'm not sure why I even decided to write this blogpost in the first place. 

(As a quick aside, if you were to argue the journey must only have Oyster cards used for public transport on this journey, you can make the overall distance even greater. Take the Gatwick terminal shuttle; take a flight to Singapore - 10,845 km between Singapore Changi Airport and Ware. But that's not the main focus of the post - theoretically you have so many combinations possible from this point that it's pointless arguing.)

The unfunny satirical "comments" section:

A truly exhilarating blogpost, one of the finest - some tabloid, maybe

I tried this trip once, it wasn't at all entertaining! Far too much greenery and too few coffee shops - gentrified tourist 

How are you still writing this blog? - grumpy stranger

ENTER THIS CONTEST AND WIN A FREE iPAD! - spammy ad

Did you really write a whole blogpost about this? You should have just googled it - another grump