Bizarre IQ Routes behaviour

[MrT]

Yesterday when I was travelling to Marlow there was some bizarre routing at J4 on the M40 and it is reproducable on both the 940 and TT Route Planner.

If at 11:00am on Monday, you are exiting the M40 at J4 Westbound, you are told to stay in the left lane on the exit slip road and directed to take the double lane that filters off left to the A404 Southbound which is the correct approach for the road design.

If 11:30 am on Monday, you are exiting the M40 at J4 Westbound, you are told to stay in the right lane on the exit slip road and you come to the main roundabout, you are then told to turn left on the roundabout cutting across into the fast of the two slip lanes that you would have been instructed to take if you had been there 30 mins earlier.

These two different approaches seem to be affected by various times throughout the morning, taking the right lane then cutting back across is not to be recommended in fast busy traffic.
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Drivelux

[PaulB2005]

Might help if you also mention where you are coming from....

I've tried to replicate this as best as possible but can't make it do what you are saying at 11:30.... It always comes off at J4 (Handy Cross) then straight down Wycombe Road.

[MrT]

At exit at J4 from the Westbound M40 when you approach the roundabout and there are four (maybe 5 Lanes), the two left lanes are separated from the roundabout and act as (traffic light controlled) slip roads onto the Southbound A404 and do not actually join the roundabout. The right hand lanes on the exit slip go onto the roundabout itself. The are islands between the two left and the other lanes. You can seen the separate routes on the TT maps if you zoom right in.

I have copied the "wrong" route below with the correct route scribbled in green. Depending on the time you exit at depends which route it chooses. Traffic on the "green" route would not be expecting traffic to exit from the roundabout route as it is traffic light controlled and on the orange route, you would be expected to go round the roundabout.


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Drivelux

[DennisN]

This looks like a bit of bad info in IQ Routes on your map version. I wonder how many boy racers have in the IQR history period jumped the green line queue by buzzing onto the roundabout and quick left? Or perhaps simply at some times, the green route actual queue is longer than the theoretical roundabout?
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Dennis

If it tastes good - it's fattening.

Two of them are obesiting!!

[PaulB2005]

Could be IQ Routes then. It might know the slip road is busier at certain times.

If i try i get the red line below.

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