Transcription
That's why I ignore satnavs when I go to an airport. What the satnav is telling me is the fastest route on average. On the way home, that's pretty good.
On the way to the airport, I ignore the satnav and take A roads. Why? Because my brain also factors in. I did this instinctively before I realized what the maths was. The A road will always be 20 minutes slower, but unlike the motorway, where if a lorry jackknifes at crack-it lane, I'm basically there all morning, the A road will never be so significantly slower that I miss my plane. The motorway has a higher average, but a far more extreme variance. The A road also has higher optionality. I can turn off it if there's a problem and try route C or route D or route E. On the motorway, I'm effectively trapped. Okay, unless you've got a 4x4 vehicle and you're prepared to drive through a fence, there's really no escape.
It's an interesting question, by the way, in motorway design, why nobody spotted this problem. A proper motorway, really, is designed for optimal conditions. What they forgot to include is little emergency exits if things go badly wrong.