What are these motorway road markings?

[LunarOne]

I'd like to think that after 22 years of enthusiastic driving, I could be called a driving enthusiast. I think I know a fair bit about cars, roads, vehicle dynamics and judging by the amount of truly shocking driving I see on an almost daily basis, I would even dare on PH to label myself as an above-average driver.

One of the little things that have puzzled me over the years, are those repetitive C-shaped marks that I often see on motorways running along the lengths of some or all lanes. It looks like they may have been left by some sort of tracked vehicle, but it's unimaginable that road workers would leave such defects in the road surface after working on them. They stick out of the surface enough that your tyres rumble if you drive over over them!

As I was stuck stationary on the M4 near Maidenhead this morning, I took the opportunity to take a quick photo. I've marked the marks I'm talking about in red:



So what causes them and why are they there?

[phil y]

Looks like remnants of temporary lane markings, they use stick on cats eyes when they're doing roadworks

[LunarOne]

I thought about that but dismissed the idea because the marks seem too close together. Perhaps you're right though...

[Peanut Gallery]

I second the proposed motion of road markings, with the possible addition of one row is cats eyes stuck down, the other row is lane barricades glued down. (sort of like traffic cones, but slightly more permanent) Regarding how close they are to each other, I have seen them really close, so that lines up!
I have seen them heat up the base of the barricades and then use that to melt them into the tar, which would leave a small dip when they are broken off again.

[anonymous-user]

Are there overnight road works/carriageway closures? They look to me (I'm in the traffic management game) like sockets for the removable/"pop-out" TM cylinders which get installed in advance of lane splits for contraflow reasons etc. If they're permanently installed, they may be in a location that is closed quite often?

[LunarOne]

OpulentBob said:

Are there overnight road works/carriageway closures? They look to me (I'm in the traffic management game) like sockets for the removable/"pop-out" TM cylinders which get installed in advance of lane splits for contraflow reasons etc. If they're permanently installed, they may be in a location that is closed quite often?

I haven't seen any works on this section of the M4 for some time, although these things aren't confined to that particular motorway. I see them often on the M40 as well. I rarely also use the M3 between Basingstoke and Bagshot or the M25 and I've seen them there. They aren't depressions, they stick up from the surface by a few millimetres, so you do feel them. At higher speeds it's just a rumble, but at lower speeds the car literally moves vertically over each mark.

[Vlad the Imp]

As per OpulentBob's comment, they're the sockets for traffic management cylinders. Basically it's a hole that's been filled with some bitumen to keep water out of the asphalt, there's probably a bit too much bitumen, hence the bump when you drive over them. The surface in L3 is old on that bit of the M4 so there's every chance that they've been there for 20 years and as they're in Lane 3 they were probably put in as part of a contraflow.

Sad I know but I'm a professional tarmac spotter.

[Piersman2]

As above, they are remnants of road works from about 5 years ago when they had narrowed lanes up and down the whole damn M4 between London and Reading where they were doing some kind of phased upgrades for about 2 years.

[Vlad the Imp]

If you thought that was bad, wait until the real fun starts in March 2017, Managed Motorway works from M25 to Junction 12 for 5 years! That said M3 traffic actually flows better while the roadworks are on so it might not be too bad.

[LunarOne]

Vlad the Imp said:

If you thought that was bad, wait until the real fun starts in March 2017, Managed Motorway works from M25 to Junction 12 for 5 years! That said M3 traffic actually flows better while the roadworks are on so it might not be too bad.

Time to find a new job then! Thanks for the very informative posts!

[Riley Blue]

Vlad the Imp said:

If you thought that was bad, wait until the real fun starts in March 2017, Managed Motorway works from M25 to Junction 12 for 5 years! That said M3 traffic actually flows better while the roadworks are on so it might not be too bad.

If the experience of those using the M1 from J28 northwards has been anything to go by, it'll be an absolute nightmare.