Peter Heather wrote:

It isn't just a bus lane; it's a lane for 'priority traffic'. It can be
used by lorries and motorcycles as well as any buses that are using the
by pass.

Sounds like most traffic except cars; is that about right. That would
make more sense than a purely bus lane; there are a lot of HGVs using
the bypass, but very few, if any, buses.

And it doesn't take away road space from other traffic as it
is an additiional northbound lane.

I was talking more about Bus Lanes in general, where one lane is
generally taken away from general traffic, to make room for them. Have
I understood you correctly; there is a northbound priority lane, but
not a southbound one? What is the reason for that?

The bypass has one lane for general
traffic in each direction and thus matches the road network to the
north and south and therefore has the same (or more) capacity as the
rest of the network.

One of the main benefits of the new road is to get the bulk of the
through traffic out of the town centre and to let it get back to being
a proper town centre.

What seems strange to me is that there still seems to be almost an much
traffic on the main road through the town centre, despite the fact that
there is also a considerable amount on the bypass. It seems almost as
if we have gained extra traffic overnight, which surely cannot be the
case. I was epecting to see a major reduction in traffic on the main
roadd yesterday morning, and that just wasn't the case.

The congestion at the north end of the bypass
(for northbound vehicles) will not be cured permanently until Purley is
sorted out, as traffic often queues all the way back into Coulsdon.
However, some of the current congestion may be due to the need to fine
tune the signal timings once the traffic has settlled down into its new
patterns and everyone has got used to the road. That often takes a
couple of weeks until some drivers eventually get to understand the
layout and stopped dithering about.

That certainly sounds possible; I do hope the situation yesterday
morning was not typical of how it is going to be in future.

I still haven't been able to take a look at the bypass in daylight yet.