car driving

there is a street branching into 2 streets. Only one of these 2 streets leads to a gas station. On every street there is a person standing. One of these 2 people is a liar ( everything he says is a lie ) and the other person is not a liar ( everything he says is true. we do not know which one is the liar from these 2 people.

a Lost car driving by on an empty tank, The car is now at the point before the street branches, The driver can only ask ONE question to only one of these 2 people about the right direction to the gas station.

what would the question be?

Hint : That question could be asked to any of these 2 people and the answer should tell the driver the truth.

just a quick one, i was driving back home late night!!!I was speeding 120 on the street with speed limit 80 ,then a flash came from a car driving in the next line next to me...im always aware from parked cars but this jackass was in moving car.What the hell?Thats totally new to me...is it possible ?Radar in a speeding car to flash you?...how will they estimate the speed ???I thought its some qatarian bored teen didnt have nothing else to do...