M18 - M180 roundabout

[Gav]

Looking at the satelite photo of this junction -

it would appear that originally there were three lanes on the M180 coming to and from the roundabout was that the case ever ? Three lanes from the M180 onto the roundabout ?

[A303Chris]

Looking at the satelite photo of this junction -

it would appear that originally there were three lanes on the M180 coming to and from the roundabout was that the case ever ? Three lanes from the M180 onto the roundabout ?

Google Streetview from January 2021 (This Year) shows it as a three lane approach

[jackal]

Entry to the M180 has been two lanes off the roundabout plus left turn filter for at least 20 years.

The terminus of the M180 was for a long time one lane onto the roundabout plus left turn filter, which was pretty stupid given the road was three lanes as far back as the M181.

In early 2015 it was changed to three lanes onto the roundabout, with the filter lane retained. But Highways England giveth and taketh away, and also signalised the eastern side of the roundabout. As far as I know that remains the layout.

Both filters were given physical separation (kerbs and bollards) at the same time, originally having been paint jobs.

[the cheesecake man]

There was of course a reconfiguration when the services opened.

[XC70]

And the s/b M18 to M180 filter was added about 5 years ago too. To do this they had to enlarge the roundabout with significant earthworks on the inside of the roundabout. In all this of course they never signalised the exit from the services, meaning that it is a pain to get out of at peak times and queues right back down the hill on the approach. Better now it is dual carriageway, but still poor.

[XC70]

Entry to the M180 has been two lanes off the roundabout plus left turn filter for at least 20 years.

I think that is incorrect. The earthworks mentioned by me above were needed to achieve 2 lanes and filter onto the M180. Before that I think it was 2 lanes and no filter but I might be wrong. It was definitely not 2 lanes and filter....

[Stevie D]

And the s/b M18 to M180 filter was added about 5 years ago too. To do this they had to enlarge the roundabout with significant earthworks on the inside of the roundabout. In all this of course they never signalised the exit from the services, meaning that it is a pain to get out of at peak times and queues right back down the hill on the approach. Better now it is dual carriageway, but still poor.

The M18 S-bound to M180 filter was there in 2008 when Google drove the road, so a lot longer than 5 years ago.

[XC70]

Ok. I can see that now. Thank you.

There was a filter from the M18 but by the looks of it only about 1 lane round the roundabout. So in a more recent works they widened the inside of the roundabout and now there are 3 lanes going round the roundabout with 2 going off along the M180.

[booshank]

Seems rather perverse that the M18-M180 interchange is of poorer quality than the M180-M181 interchange.

[jackal]

Seems rather perverse that the M18-M180 interchange is of poorer quality than the M180-M181 interchange.

I would say it's a three-arm versus four-arm thing, except the services opened long after the roundabout. Though perhaps they were planned.

A better design with no more structural content would be a parclo with a freeflowing loop for M18 to M180. This could have been built as a trumpet with the extra arm added with the services. But such things are verboten on roundabout island.

Even as is it's far from the worst case of a motorway or expressway terminating at a roundabout, with two well-aligned filter lanes and reasonable capacity through the roundabout after the 2015 improvements.

[c2R]

Seems rather perverse that the M18-M180 interchange is of poorer quality than the M180-M181 interchange.

I would say it's a three-arm versus four-arm thing, except the services opened long after the roundabout. Though perhaps they were planned.

No, they weren't - there's space for proper on-line services just south of the interchange (see: Hatfield services)