Simple: a new knowledge. The commercial SatNavs know the one way streets. That is a strength: you don't need to know them, but also their great weakness. Their routing algorithms assume that you can only traverse a one-way street in the direction the arrows point. That is, the collection of streets, the graph, is a directed graph. Experts in the city can use this to their advantage. By knowing exactly which little one-way street they can nip down, they can come up with a more optimal routing through the city. For example, ask a SatNav how to get from Kingsdown to Cheltenham Road, and it will come up with two solutions, neither of which work well at 17:10 on a weekday.
1. Cotham Brow (busy), Arley Hill (long queue)
2. Horfield Road, Park Row, Jamaica Street.
A driver with The New Knowledge will know another solution. The one way bit at the bottom of Nugent Hill. It does bring you out into Arley Hill, but if there is a big traffic jam., you've missed it.

This blog strives to avoid making any accusations that could be considered libellous, and therefore does not state whether this taxi, the Jaguar with the Bristol City Taxi #2036 license plate on it, has done any such action. Instead, we will say: if they had done something like that at about 17:00 hours on Thursday December 11, 2008, they had better not have had their SatNav unit turned on, because those little units not only make suggestions on where to go, they record where you went. So if this taxi had driven the wrong way down the Nugent Hill one-way-section, the car would remember the fact.
Which is another piece of knowledge you need to remember, isn't it. The SatNav may be your friend, but only your friends can betray you.
[Reg # PX55SVL]





