my questions answered
Last Saturday I went with Laura on a day visit to N Kent, so for the second time recently I got to experience the M25. Usually that would be a prelude to talking about congestion but not this time. So I had the head-space to concern myself with a lesser evil. There's a long light-coloured section in the SW quadrant of the M25 where the road surface is particularly unpleasant to drive on. The tyre noise is much louder than normal and the van shakes as it passes over regular joints. I'd always vaguely wondered why this was.
Turns out that this section of the M25 has a concrete surface (as opposed to a tarmac surface). The definitive discussion on the topic is here:
Very informative it is too. Here's a post that mentions my stretch of the M25 specifically, though it begins by talking about a notorious stretch on the A27 that I also remember very well.
The A27 Chichester to Havant was the worst for sideline noise ever in the country. It must be due to the small detail of the fines in the concrete, in that you get different noise performance from different sections. I remember being in the villages half a mile to the south and it sounded like a continuous jetplane noise. However, it wasn't so bad when in cars driving along it.
In contrast the M25 in Surrey from Reigate round to Cobham, which was originally concrete D3M, and widened out to concrete D4M, is a real thumper and whiner to drive along nowadays (if you don't know the stretch you can think you have a puncture), but not so bad in the country alongside.
For a long time the MoT/DfT always went out for two quotes from main contractors for new motorway construction, for asphalt or for concrete top surface, and invariably chose the cheapest on each section. Because the price of the bulk materials is quite dependent on haulage costs from where the relevant local depots for each type of material might originate from, this can give the differential pricing which favours one or the other in different places.
What surprises me is that much of the US Interstate network is concrete surface, yet they seem to have cracked this form of construction and do not get anything like the noise nuisance we do in the UK, either in-vehicle or sideline. I don't know how they do it (although I have asked them more than once).
The other motoring-related question that preoccupied me was: Why do you need to ask for a VAT receipt? (You would be right if you imagined the slightly exasperated tone of someone who had recently forgotten to ask for a VAT receipt while on a business trip.)
Informatively discussed below. No exciting revelation of dark conspiracies, though. Dishing out separate VAT receipts would cause litter, because most people don't need them. But few businesses (supermarkets aside) have tills that are able to combine the card receipt and VAT receipt onto a single bit of paper.
Some contributors pointed out that there were rather more pressing things to moan about than having to ask for a VAT receipt. I promptly disowned my former moaning on this subject. I felt it had been sublimated into a laudable thirst for knowledge.