Q:

How to cancel job interview without burning any bridges? 

TL;DR I agreed to a job interview and now I don't want to go; how do I explain it to the HR without burning the bridge for further applications to the same company? 
Context:
Some time ago I applied for multiple job positions, as I perform very well in my current company and wanted to get some perspective on how much raise I can ask for while being periodically evaluated. 
HR from one company called, we agreed on the interview date, it's next Monday.  I received an invitation email and then realized that the office I would work at is 1-hour drive from my place of living, and I definitely don't want to travel 2 hours a day (on good traffic days) to and from work.  I do know it's my bad that I did not consider it before applying and agreeing to meet.  
However, I like the company culture and projects very much and I think I might apply there again in the future, preceding it with the relocation (I rent a flat, it's not THAT big of a deal, just definitely not now, as I relocated recently and like it so far). 

Difference between my question and possible duplicate is that I (in my opinion) don't have an honest excuse to cancel the interview, while OP in the other question does - he decided to stick with his current company.  
Another difference is that it leads to the great answer by ItWasLikeThatWhenIGotHere. 

A:

Don't think of it as skipping the interview - you're politely declining one particular opportunity. 

Dear HR,
I am writing to let you know that I will not be continuing further
  with my application for the [position]. 
Thank you for your consideration of my application, and apologies for
  the late notification.  I hope we can discuss other opportunities in
  future. 

Keep it simple - interviewers are used to having cancellations, and if it's done politely and in advance of scheduled interviews this will count in your favour. 

A:

Just be honest.  Tell them how much you like them, but that the 2 hours daily travel is a deal breaker for you and you just realized that. 
Who knows - they may move their office some day or find some other opportunity for you. 
Maybe they (and you) can live with with a day or two weekly at the office and some home office days, maybe they can come up with something else.  
Or they may agree that 7 hours work day could be fine for you so they compensate 1 hour and you go with 1 hour. 
If you give them the real problem - they may be able to find some real solutions.  No company will just throw away a good and honest engineer, trust me :). 

A:

I (in my opinion) don't have an honest excuse to cancel the interview

Yes you do.  Your honest, actual reason is that you don't want to work at the company because you've realised the commute is so long.  That's a perfectly good reason.  Obviously, you're sorry for not noticing that sooner, etc.