Smallest and largest freeflow interchanges

Going on holiday? Just returned with pictures or news? Found an interesting website? Post everything international in here.

Moderator: Site Management Team

User avatar
jackal
Member
Posts: 7539
Joined: Tue Jan 08, 2008 23:33
Location: M6

Re: Smallest and largest freeflow interchanges

Post by jackal »

Chris5156 wrote: Thu Sep 24, 2020 20:58
booshank wrote: Thu Sep 24, 2020 20:16 The loop is nothing unusual in size, but the left turn and semi-directional right turn movements of the N1 - N4 interchange north of Pretoria are pretty large (2.07 km from diverge to merge northbound). It's interesting how they've used separate bridges for the two right turn movements so that N1 S to N4 gets a much better alignment.
That's surely because it's laid out with the intention that it'll eventually be turned into a four-way junction, with N4 continuing east and forming a bypass around north-east Pretoria. The land appears to have already been acquired for the rest of the junction and the property lines are clearly laid out to allow for the left-turns.
I don't know the original intention, but a decade ago there was a plan to extend it as an eastern bypass of Pretoria, all the way around to the R21 south of Nellmapius Drive: https://www.google.co.uk/maps/@-25.8653 ... a=!3m1!1e3

The southern section of the R80 is a series of obviously unfinished junctions, most notably where the westbound mainline circumnavigates a tight loop! https://www.google.com/maps/@-25.704410 ... a=!3m1!1e3 Here the freeway is cobbled together from two perpendicular arms of an unfinished cloverleaf. While they've long given up on the western stretch towards Hartbeespoort there were recent plans (now abandoned) to extend southwards as far as the N1 Johannesburg Western Bypass.
booshank
Member
Posts: 610
Joined: Thu Apr 28, 2011 19:05

Re: Smallest and largest freeflow interchanges

Post by booshank »

Chris5156 wrote: Thu Sep 24, 2020 20:58
booshank wrote: Thu Sep 24, 2020 20:16 The loop is nothing unusual in size, but the left turn and semi-directional right turn movements of the N1 - N4 interchange north of Pretoria are pretty large (2.07 km from diverge to merge northbound). It's interesting how they've used separate bridges for the two right turn movements so that N1 S to N4 gets a much better alignment.
That's surely because it's laid out with the intention that it'll eventually be turned into a four-way junction, with N4 continuing east and forming a bypass around north-east Pretoria. The land appears to have already been acquired for the rest of the junction and the property lines are clearly laid out to allow for the left turns.
.

Yeah, seems obvious looking at it again! I still like it as a trumpet though. It's likely that N1 southbound to N4 westbound is going to be markedly the least busy right turn movement so a loop makes sense with a better provision for N4 westbound to N1 southbound.

It's not really clear where the completed road would go as it looks as though development and a ridge of hills form an east-west barrier to an outer eastern bypass.

South Africa must have one of the world's highest ratios of incomplete to finished interchanges, with Pretoria at the epicentre!
User avatar
jackal
Member
Posts: 7539
Joined: Tue Jan 08, 2008 23:33
Location: M6

Re: Smallest and largest freeflow interchanges

Post by jackal »

booshank wrote: Tue Sep 29, 2020 11:34 It's not really clear where the completed road would go as it looks as though development and a ridge of hills form an east-west barrier to an outer eastern bypass.
You can see most of the route (marked K54) here:
GFIP - Copy.JPG
mattling
Member
Posts: 403
Joined: Tue Apr 20, 2004 13:07
Location: Coventry

Re: Smallest and largest freeflow interchanges

Post by mattling »

Junction 2 of the Coventry Ring Road used to be fully free flowing and extremely compact. The original layout is shown on the Roads UK article. Hales Street is now two-way (for buses only) which means there's a give way for the movement from the Ring Road to Hales Street north.

https://www.roads.org.uk/articles/coven ... /route-map
User avatar
Alderpoint
Member
Posts: 1682
Joined: Wed Aug 19, 2015 14:25
Location: Leamington Spa

Re: Smallest and largest freeflow interchanges

Post by Alderpoint »

That route-map is incorrect. There is (and never has been) a road from Junc8 intowards the city centre, and there is (and always has been) a road from Junc1 intowards the city centre.

(There are also a few other changes at J4&J6 in the last 10 years.)
Let it snow.
Post Reply