On 22 April 2012 08:41, Martin Vonwald <imagic....@gmail.com> wrote: > Can we agree on that for narrow roads, where one can not determine the > width exactly we would recommend: > lanes=2 > width=4 > source:width=estimated > or > lanes=2 > est_width=4 >
I've had a look for uk guidance as the uk's ordnance survey was mentioned, and a lot of older uk advice appears based around a now historic view that 'cars = saloon cars' and were 1.8m or less. If cars were assumed to be 1.8m wide then implied OS figure of 4m for two lanes makes sense. But saloon cars are no longer the 'standard' car, in the uk they've more or less been replaced by hatchbacks & 4x4's. If we look at best selling cars in the UK (and I assume Europe) we have to assume car widths (with mirrors) are now just over 2m, which I'd round up to 2.1m. Therefore I believe a road with a width of 4m should be mapped as a single lane. I'd argue you'd need at least 4.3m before a road could now be considered narrow, or car only, 2 lanes. Though I'd think a road 4.3m wide would fall under the 'lanes=1.5' idea Following image was taken from a uk guidance document, although as I've said above it appears to rely on the now incorrect idea that car widths can be assumed to be 1.8m. I think it's good advice if you add on 0.2m for each car lane. http://bit.ly/IkVv9B Realising this is a far more complex issue that I first thought. Personally I don't I'll be adding widths. I'll simply add the lanes based on what seems obvious to me. After reading through these emails I'm beginning to think the lanes=1.5 would less confusing for narrow two lane roads. Jason
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