Spiral roundabouts (or gyratories), like the Tushmore spiral roundabout in Crawley (the one with all the traffic lights on near Sainsburys), can at first look very tricky, but once you know how to deal with them you may change you mind :-)
Well on the Tushmore roundabout there are a couple of key factors to consider:
The Traffic Lights
There are lots of sets of traffic lights on the roundabout and they are all very close together, so when you are on the roundabout always anticipate the lights changing and be prepare to stop if they do change (remember a steady amber light means stop unless it is unsafe to).
Sometimes it can be hard to work out which traffic light applies to you and hard to anticipate them changing while also being aware of the car around you. The key to successfully be able to do this is to drive at a speed where you will have time to see all the traffic lights and work out in your head if they apply to you or not, at first you may need to drive a bit more slowly than the other cars so you can do this successfully, as with any bits of driving the more you do it the more confident you will become.
Ultimately, personally, I would never drive more than 20mph in 2nd gear on this type of roundabout, if you go faster that this it will increase your braking distances so give you far less time to react to traffic lights changing and give you less time to deal with the other car, who may change lanes suddenly or straggle the lanes in error.
Rule 1: On each approach there are 3 lanes, as such we can apply this rule:
Left Lane = Exits 1 & 2 (Example - *TEST ROUTE*)
Middle Lane = Exit 3 (Example - *TEST ROUTE*)
Rule 2: The lanes move one to the left after each set of traffic lights (excluding the set on approach to the roundabout). So if you are in the right lane at a set of lights, you should be in the middle lane for the next set, and then the left lane for the next set of lights.
Rule 3: If the road signs on approach say there are two lanes for the same exit then you should normally go for the left most lane, the 'normal driving lane' the right most lane is for overtaking. i.e. if M23 was middle and right lane then you normally use the middle lane unless overtaking.
The key thing is to stay in you lane and not to 'straggle' the lanes as there could be a car next to you that you could collide with. So once you have picked your lane stick to it and drive at a speed in which you can comfortably keep in you lane. Often people find the most difficult thing to do on this roundabout is turning right, as you will need to change your positioning a few occasions.
Below you will find a diagram of a spiral roundabout, the orange line shows the road positioning required to turn right, note the way you just have to stay within the white road markings and the lane will take you to your exit.
Lets look at an example, we are approaching from the Ifield roundabout, aka the 'wiggly bridge' one, turning towards Town Centre.
The road sign tells you to use the right lane for Town Centre, check mirrors and blindspots and move into the right lane when safe.
The road markings confirm that you need right lane for going to Town Centre, keep in the right lane and when safe go through the first set of traffic lights.
At the second set of traffic lights the lane starts to move, see the white lines on above image, the rights lane is now starting to move left to become the centre lane. Check your middle and left mirror for any following traffic straddling the lane and then folioing the road markings into the centre lane.
When you reach the third set of traffic lights you should be in the middle lane, now look at the road makings again (as indicated by the arrows above) and see how your lane starts to move over the the left again, soon to become the left lane.
By the time you get to the fourth set of lights you should be in the left lane, the road markings confirm that this is the correct lane for Town Centre.
Now keep to the left to take the exit for Town Centre, the road sign (as above) confirms the exit for Town Centre.
Yellow Box Junctions
As you will have seen from the above pictures the roundabout has lots of hatched yellow areas on it. You must not stop in these areas, they are there to keep parts of the roundabout clear to help with congestion, stopping in the areas could cause a traffic jam. Before you enter the yellow areas you need to be 100% sure that you can fully cross it without stopping in it, if you don't think you can fully cross it without stopping in it then do not enter the area.
There normally no need to signal to come off these roundabouts, as most people can tell where you are going by the lane you are in. The only time you might need to signal is if you feel like someone would benefit from it, perhaps if a pedestrian was looking to cross the road on the exit you were taking, they are unlikely to know where you are going by your lane position, so putting a signal on will tell them you are coming their way, so they are less likely to start to cross the road.
If you think you have got in the wrong lane then normally the best idea is to just 'go the wrong way' staying in the same lane, so if you end up in the lane for Brighton then take the Brighton exit, DON'T drastically change lanes. Changing lanes drastically can be very dangerous because on such a busy roundabout there are highly likely to be cars next to you all the time, so you could collide with them. This roundabout may seem complex at first but like anything with driving the more you practice it the more confident you will be with it. Before attempting this roundabout you need to be happy to try it and should be dealing with 'normal' roundabout independently, be able to deal with traffic lights and box junctions and also use to dealing with lots of traffic, without practice of these skills dealing with this roundabout will be very very difficult indeed.
Have a look at the below videos for a in car demonstration of how to do the roundabout.