Friday, 27 January 2017

Exam Questions

So, AdExcel put a series of questions into an exam paper that are designed to imply people cycling cause pollution. Here is the central quesion, but there is more to it here.

The premise seems reasonable, until you think for about a millisecond. Wait, during a ten minute journey there's an average of 3 cars behind? No, sorry, not in any world I've ever experienced!

So, I thought we'd take a look at something that looks like reality a bit more. Here's a clip from a morning this week, showing traffic coming through Cherry Hinton into Cambridge.

And here's the clip with a variety of start points which open YouTube in a separate window.
Go HD see * at bottom

At the start
0:42 From Perne Road
1:56 From Cherry Hinton High Street

So we'll start with some simple questions.
1. How many people riding bikes are holding up this queue of cars?
2. How many people driving cars are holding up other people driving cars?
3. How many cars are single occupancy?

And some answers, so those hard of analysis capabilities (like maybe some AdExcel exam setters) might keep up.
1. I'm hard pressed to spot a single rider holding anyone up here. The clip shows over a mile and a half of queuing traffic, without many people riding at all. And where there is the odd rider they aren't interacting with motor traffic at all.
2. Pretty much all of them.
3. The figure for rush hour traffic in Cambridge is 1.2 people per car (near the bottom of here). In other words, in every 5 cars there are 6 people. That's 4 cars with one person, 1 car with two.

Then, some more complex questions.
1. Speculate why there are jams like this if they are not caused by people riding bikes.
2. If we halved the number of people driving here, how much less carbon dioxide would be pumped into the air?
3. What do those people who would be driving do instead?

And again, some answers.
1. Well, this map shows the three jams in a bit more detail (in red/purple). They are coming up to intersections. That is, they are caused by two lines of traffic having to merge and/or manoeuvre around each other. So, it's all about people driving vehicles that are large enough to require management when they intersect. Not an issue that faces anyone on a bike.
2. I've not done the maths here. Anyone not think this number will completely overwhelm the number the AdExcel paper comes up with? It does make it look slightly ridiculous.
3. There are a number of pleasant parallel cycling routes (once I spotted a watervole!). I use them often (in reverse) when travelling under 10 miles. They are well used, yet have no jams.That's because the "vehicle" (bicycle) isn't large and doesn't require management when many come together.

It does beg the question, what is going on with AdExcel such that they decide to put this "alternate" analysis that implies an "alternate fact", where they could do some equally good maths that actually supports the real evidence.

* How to go HD.