Car drivers are more concerned with heavy congestion and traffic than of crashes, according to an AA/Populus survey.
A quarter of the 23,000 drivers polled said congestion was the greatest worry when they had to drive for more than 200 miles.
Having an accident was the second most common worry on long journeys with 17% of drivers worrying about this the most.
Top long-journey stresses differ across the country as well as across age groups.
AA president Edmund King said: "The last thing anyone wants is for something to go amiss on that journey and end up ruining their summer plans.
"Congestion, accidents and breaking down are the top trio of nightmares drivers fear."