It’s quite enforceable.
Your intention does not matter. Your actions do. The police (or prosecutor or judge) are free to take account of your stated intent (or their assessment of it), but you are nonetheless in violation once you use the street for through traffic.
Since small streets almost have a stop sign where they join a major thoroughfare, it would be easy for a policeman to “set up shop” at the end of the street, and watch for cars that enter the street and pass straight through. A friend lived on a residential street that joined two oblique thoroughfares. (Rushed commuters used it to bypass several traffic lights in the commercial district around the major interesection, and sometimes endangered children walking to school) The police periodically set up a very successful “thru traffic” [sic] trap there.
You could obfuscate your intent by pulling into a driveway (leaving, then re-entering the street) but I doubt most rushed drivers who flout traffic regulations in their hurry would inconvenience themselves this way. Again it becomes a matter of what one actually does, not what one could do.
I was once charged with commiting a similar infraction which may clarify the situation: Late one evening, I was driving through the deserted center of of my small town. As I slowed for a stop light, I noticed what appeared to be a friend’s car (a rather ostentatious pre-oil embargo Cadillac) parked at a corner gas station. Since he now lived 3500 miles away, I was surprised, and pulled into the gas station to check the license plate.
It took only a moment to confirm that it was his car, and (the lot being crowded with cars awaiting repairs) continued straight to the other exit. A police car behind me observed this, and pulled me over. He believed my story (I recited the owner, make, model, and license plate of the car I’d checked) . Nonetheless, it’s unlawful to bypass a traffic light, and he wrote a ticket. (The judge dismissed it, grudgingly and with a warning, but I’d understand if hadn’t.)
I think we can all agree that allowing drivers to use a gas station or parking lot to bypass traffic lights defeats traffic control. The danger of allowing the most hurried drivers to funel down residential streets may be less obvious, but it is nonetheless real. I support such residential ‘police traps’.
Incidentally, it’s always seemed to me that many people who delight in inventing excuses why traffic laws are unenforceable complain for years when reality proves them wrong. The notion of considering the intent of the law seem beyond them.
[Then again, the appeal of the ‘legal loophole’ is undeniable. Feudal European laws were often softened by illusory loopholes (quirks which would rarely, if ever, apply). Wise lords knew that allowing one serf in 100 to ‘get away’ with a minor infraction created a general impression of fairness.]