Despite the stereotype that BMW are douchebag drivers, don't use their turn signals, cut you off, bad parking, etc. I find that the average bmw driver I see on the road are fairly courteous like you said and not at all aggressive like others make us out to be.
If I'm being completely honest - many Audi drivers (not all) are the worst followed by Merc drivers if we're comparing German car owner driving etiquette. One thing I do notice, however, is the entry level models such as the A3/A4, 320i, C300, CLA tend to be attract the worst drivers of them all and owners like to think they own the road.
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