If his back pain is due to sciatica then he should do Physiotherapy for 7- 10 sessions to reduce the pain. It is not advisable to travel long distance in sitting position.
If it is inevitable then he can use lumbosacral belt and seat belt while travelling to avoid jerks.
He should take breaks in between for every one hour while travelling.
Getting down from the car for every one hour to relax the muscles.
Next Steps
He can use Volini gel or spray provided he is not allergic.
He should take hot water fomentation for 15-20 minutes twice a day.
He should do back stretching and strengthening exercises with proper guidance.
Health Tips
He should consult a Physiotherapist as early as possible.