I thought it was overtake if you passed on the left side of the car and undertake if you passed on the right side (in US but the opposite in UK). I also think that undertake is a UK expression and not a US one.
MMFAN - I'm with you here and have been both overtaken and undertaken quite frequently in US (undertaking is not allowed in UK - you have to overtake only which is on the right side of the car) which is one of the reasons for the tip to check BOTH mirrors before changing lanes when driving in US! You don't need to do this in UK!
Gosh, this is getting very complicated!
Blott
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