If your in a dedicated left turn lane...

[Adasta]

There's something to be said for not indicating in this situation: your hands will be on the handlebars and far closer to the brakes should you lose control.

 

[Garz]

Also there are roads that fork in such a way that if your in the wrong lane you cannot switch lanes easily.

 

[youngoldbloke]

The basic problem is that many (most?) motorists have no idea of the concept of the primary position for cyclists, and wrongly believe that cyclists should always be as far to the left as possible, so that when we adopt the primary position we are obviously being bloody minded and obstructive, (and in this situation probably continuing straight on). Education, education, education! If you are in a dedicated left turn lane you should obviously not need to give a left turn signal, but as others have said in some circumstances it may be safer to do so.

 

[Davidc]

No signals are compulsory (I know some should be) and I've learnt that they should be used to help and inform others (or so said the defensive driving instructor).

What's the point (in/on any vehicle) of indicating that you're going the only way you're allowed to? It's more likely to confuse than inform.

Unfortunately you had a brain dead moron in a car behind you, and there's no known way to prevent that happening.At least it wasn't the variety that goes round with its eyes closed.

 

[Camgreen]

Don't think I'd feel the need to indicate either, whether cycling or in the car. Again it's all about hazard perception; the driver upon approaching the roundabout should anticipate (and rightly so) that you might turn left (particularly as it's a dedicated left turn lane) and should hold back accordingly. Seems to me to be a case of an impatient and inconsiderate motorist putting your well being at risk unnecessarily.

 

[661-Pete]

Sometimes I do, sometimes I don't.

I'll always signal if there's someone waiting to come out. Courtesy. And if there are pedestrians about to cross the left-hand road. Safety. I'll avoid signalling if there's an HGV or bus bearing down me from behind. Keeping its driver guessing could be a life-saver, one day. If both situations occur together, well I just have to choose what's best.

and another off the top of my head was a polish driver in the early hours one morning setting off to meet up for a ride in the lakes; he beeped when overtaking too even though there was not a sole around!

I think that would be most unlikely, even in the Lake District!
IGMC