For road design:
The turn arrows to me look weird, like they were drawn by kids...
Some signs are also strange (such as a "MERGE" sign as opposed to just, using the pictoral sign of a lane ending)
And don't get me started on the traffic signals!! Why do the signals on the side look rather neglected (with no backplates), and why are they 8-8-8-12???? Ahhhhhh
The arrows in British Columbia are not completely unique to BC. They are also used in WA, by a few cities. I've always preferred them simply because I find them easier to comprehend.
I do not understand the MERGE sign either. So many symbols and yet they write that one out. Weird.
The arrows used in WA aren't quite the same, though, and I prefer the look. I don't like how the BC arrows have such a long straight tail and then a tiny little curve, and I think that might be part of the reason why andrepoiy said they look "drawn by kids".
Here's a comparison, with BC on the left and WA (from Bellevue) on the right.

The more interesting thing (from my perspective) about BC turn arrows is that darn near every intersection in the province uses that same exact style! In the cities around Seattle, it seems like every other city (not to mention WSDOT) has its own unique style

Also on that merge sign, I really don't get why they use that, given the whole bilingual situation and a very well established symbol that can take the place of it. You'd think that with a whole host of symbolized signs you can see throughout the province that aren't used in the US, that there wouldn't be an example of the opposite case, but here we are! I will say BC isn't the only place I've seen a spelled out "MERGE" sign though, I have seen quite a few in Minnesota when I've been there a couple times, which struck me as odd then too, though the ones there do also feature a sideways arrow at least. (
Example)