Sir - The correspondence kicked-off by Jeremy Clarkson's article (Report, December 1) is really about causation, that is, the identification of the link between road layouts, speed restrictions etc on the one hand and, on the other, a sufficiently wide sample of data (including, but not limited to, accidents) from which to draw conclusions.

Causation is complicated stuff, requiring thought and analysis of competing contributions to events. "Ban" and "spend" are much easier concepts.

No need to think, no complicated differentiating between "hazard" and "risk", just impose a speed limit, fiddle around with the road layout, and write a cheque.

Then, the next time a negligent bus driver hits a cyclist or a grossly negligent mother veers across the carriageway or a thoughtless student wanders across the lanes at a roundabout, the highways officers can say "it was not my fault". This back-covering has become the main driver for highways officers' activities. It wastes money and distorts priorities. We must get some thinking back into road planning.

Chris Dale, Oxford