Sketchplanations

Explaining one thing a week in a sketch

Hump-Back Stations illustration: an above and below ground cross-section of an urban environment is shown, displaying the rise and fall of an underground transit tunnel as it approaches and departs a station platform - allowing gravity to play its part in slowing the train down, uphill as it comes into a station and accelerating it away, downhill on departure.

Hump-back stations

A rather clever way of capturing energy as vehicles slow down is to store the energy you'd use in braking as gravitational energy. This way of storing energy is used on a number of central London underground stations by constructing the stations at the top of a small hill in the track. Once built, the hump-back-station design has the handy effect of naturally slowing trains down as they approach a station and naturally accelerating them as they leave a station. Apparently, on London's Victoria line this saves 5% in energy and helps the trains run 9% faster.

You're not always going to be able to put a slope just where you need to slow down, unfortunately. However, it makes a ton of sense for pedestrian crossings where raising the crossing to the level of the payment means pedestrians don't have kerbs to negotiate and cars are naturally encouraged to slow down.

Victoria line data from Sustainable Energy without the Hot Air, by the late David JC MacKay

Keep exploring

How to identify a Bactrian or Dromedary Camel: The Bactrian camel (on the left) has 2 humps like the capital letter B turned on its side. The Dromedary camel has 1 hump (on the right) like the capital letter D turned on its side. If you can count the humps, you know the first letter.
Point Nemo - the furthest point from land shown on the earth with the nearest three landmasses, Ducie Island, Moto Nui and Maher Island. This would be a long swim.
The Swiss Cheese Model illustration: A stack of 4 vertical Swiss cheese slices act as safeguarding protective layers, keeping a young family on the right of the stack safe from the harmful elements approaching from the left. Although the holes in the cheese slices allow penetration through some of the barrier, the multiple layers, with unevenly distributed holes, prevent harmful elements breaking all the way through.
Implementation Intentions illustration: A blank ballot paper is shown as the result of vague plan to vote at some point. A completed ballot paper demonstrates how a specific logistical plan on when, where and how they'll get to the polling station got the job done.
Phone zombie illustration: pedestrians turned zombies staring into their phones run into danger and bump into each other while crossing a road
Siphon illustration: how a siphon works draining a reservoir by running a water uphill, unaided, until it empties into a lower reservoir.
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