• trailcar,
• tralcars,
• rrail cars,
• frail cars,
• grail cars,
• yrail cars,
• 6rail cars,
• 5rail cars,
• teail cars,
• tdail cars,
• tfail cars,
• ttail cars,
• t5ail cars,
• t4ail cars,
• trzil cars,
• trsil cars,
• trwil cars,
• trqil cars,
• traul cars,
• trajl cars

The adjective form of "trail cars" would be "trail car".

The plural form of "trail car" is "trail cars".

The singular form of the word "trail cars" is "trail car"