Car turning radius calculation

[MrChips]

Long story short.... does anyone know of an online calculator to help work out dimension A in the image below?



Background is some discussions with the local planning authority on a restriction they're putting into a new development and have stated that the dimensions on their plan will prevent people approaching from the red road below, and turning left into the new development (towards the top of the image in this orientation). I'm not convinced that the turning is tight enough to fully prevent people using the red approach, especially with a relatively open environment with only single bollards on the centre islands.



Any easy ish methods for calculating whether a car could easily turn within the junction as its shown above?

[MrChips]

Thank you! From the diagram above all I can tell is it “might” be too tight to turn, not sure I can work out the dimensions.

AlmostUseful said:

, but I'd expect 4m absolute minimum radii if they're not designated as vehicle crossovers (which it doesn't look like).

I don’t really follow this but too. The council say they’ve designed it to be impossible to turn, only traffic going north-south or east-west should be do-able? It’s basically an open junction but too tight to turn, I’m just not sure it’s tight enough based on their drawings!
I’m probably over simplifying it

[MrChips]

To add some context to this (didn't want to make the OP over complicated)... to the south of the junction is phase 1 of a new development, and to the north is phase 2 which will be around 400 homes and a school.

The existing road that runs east to west is single lane, one way (from left to right), and the access road to phase 2 traverses this existing road.

This is the existing road (east to west):


And the proposed junction sits here:


A wider view of the junction:


Obviously with 400 homes and a school as part of the development, the current residents on the roads surrounding the estate are keen to make sure that the access to the northern 2nd phase remains via southern phase 1 as has been passed in the planning application. The council has designed the road layout to prevent people using the unsuitable small one way roads to cut through into the new builds and school, but there are already significant issues with people going the wrong way up the 1way existing road just to save themselves 20seconds and exit the newbuild estate quicker.

Edited by MrChips on Friday 16th February 09:09

[MrChips]

Thanks for the replies all, especially the Paint drawing mr hard-drive

Swervin_Mervin said:

Just looking back at that I don't see how they expect that to work. AFAIK you can't get quadrant kerbs with a 10mm upstand (I could be wrong), and the proposals illustrate the tactiles right up to the quadrant. You'd need a 900mm dropped kerb to link the 10mm upstand kerb at the tactiles with the std height quadrant on the corner. The radius doesn't look large enough to be a radius kerb.

Worryingly I understand all of that now, and yep, the dropped kerbs look too close to the corner to be able to have any effective kerb height, let alone a Trieff kerb.

I've asked the council for clarification. I'd assume they couldn't put a bollard on the kerbs next to these dropped tactile paving sections as it would constitute a trip hazard next to a road. I've also asked for info on who is responsible if their current plans don't work. I've already seen first hand people exiting the phase 1 of the development and turning left the wrong way up the one way street, presumably as it's "only 50yrds" and it may be a tiny bit quicker for them. If people are happy driving the wrong way up a single lane street then I'd rather the junction makes it impossible to turn rather than just awkward.

I feel like such a busybody