there is only kamma when there is an intention. action without intention is not kamma.
So if a trucker in an eighteen wheeler inadvertantly runs over you whilst he's texting his wife, then there's no kamma for you or the trucker...
nice story. but manapa already said it. the trucker's actions and my action are intended, therefore there is kamma and kamma-vipaka. it is not possible to ponder in what an effect a particular action results, that would be nothing more than making assumptions. that's all. besides there is not really kamma for
me or the trucker. when one acts intentionally
this is kamma
. when there is kamma there will be kamma-vipaka. actio -> reactio. there is kamma which leads to more kamma and there is kamma which leads to the cessation of kamma. i.e. there are actions leading to more action and there are actions leading to the cessation of action. akusala kamma (unwholesome actions) and kusala kamma (wholesome actions) means that.
best wishes, acinteyyo