Travelling allowance is given to those candidates who are qualified to attend screening test (Day 1 Testing). These candidates can claim fare of up to tier 2 AC class. You need not to produce to & fro ticket, one sided ticket is enough.
TA is applicable for only once for each service type i.e SSC ( Short Service Commission ) and Permanent Service Commission. Please note, If you have already attended either SSC or Permanent service commission SSB either in Air Force or Navy or Army it will be counted.
So you are eligible once for SSC & once for PSC irrespective of Army, Air force or Navy.
PS: Bhopal SSB & Bangalore SSB have having maximum formality for TA claim while Allahabad SSB will give you TA based on either actual ticket or permanent address as per your application.
Focus on SSB rather than TA
All the Best.