WHEN MEDICAL students become doctors, they take an oath to do no harm to those who cross their paths. The promise recognizes the power that medical folks have to muck up a person's day.

You know who needs to make a similar pledge? The jerks at the Philadelphia Parking Authority.

If they swore to wield their power with reasonableness and respect for the public, a Good Samaritan named George Echenhofer never would have been punished for being the kind of decent citizen this city needs more of.

How infuriating was his treatment by PPA? So infuriating that the normally mild-mannered Echenhofer, 45, contemplated smashing up the PPA's offices at 8th and Filbert streets.

"I thought, 'I could take that trash can and throw it through that window,' " said Echenhofer. "I felt like destroying the place."

I did, too, after I heard his story.

Echenhofer, who commutes from Moorestown, is the information-technology director at the Metropolitan Career Center, at Broad and Chestnut streets. Last Wednesday morning, he was circling for a parking spot near work when he witnessed the car in front of him strike an older female pedestrian near 12th and Chestnut.

Echenhofer pulled to the curb at 1211 Chestnut, flicked on his flashers and rushed to render aid. The driver of the other car also stopped and was visibly shaken. Echenhofer offered calm support and directed traffic around the accident scene until police and medics arrived.

As the EMTs were hoisting the victim (whose arm appeared broken) into an ambulance, Echenhofer was startled to see a parking-enforcement officer ticketing his Volkswagen.

He'd parked it in a truck-loading zone that prohibited parking until 10 a.m. The time was 9:21 a.m., so technically the ticket was legit.

But - wait - is this a joke?

"I said, 'Hey, don't give me a ticket! There's been an accident and I'm helping!' " recalled Echenhofer. "The guy wouldn't listen. He was actually nasty."

A police officer on the scene (a woman named Walsh, whose first name the Police Department didn't provide yesterday) also pleaded on Echenhofer's behalf. But the PPA officer wouldn't budge. So, Walsh called for a PPA supervisor to intervene.

Because Walsh was due in court and couldn't wait for the supervisor, she wrote a note confirming that Echenhofer had witnessed an accident and was providing information to police while the ticket was being written. She signed it with her name and badge number.

It seemed like ample proof to the supervisor who eventually arrived - a woman named V. Harper-Rahiem, who, Echenhofer recalls, said that the $51 ticket "never should have been given." But when Harper-Rahiem called her own supervisor to see about dismissing it, she was shot down.

"She seemed embarrassed," said Echenhofer. "She told me that in God's eyes, at least, I had done the right thing."

The Lord's power, apparently, is trumped by the PPA's.

Because Echenhofer hit a wall of insolence when he immediately walked to the authority's offices, at 8th and Filbert, to try to explain matters.

"I didn't want to have to come back another day for a hearing," says Echenhofer. "I thought that once the right person heard what happened, I could get the ticket dismissed on the spot."

The first clerk he talked with, though, was so indifferent and unhelpful that he asked for a supervisor, hoping that he could get a same-day hearing since he lived out of state (he says that he'd been able to get a same-day hearing in the past using that protocol). But the supervisor, he said, treated him with contempt.

"She was enjoying her power, that's all I can say," says Echenhofer. "I showed her the note from the police officer and she said,'That tells me nothing.' "

He sought help from a clerk at the Parking Bureau of Administrative Adjustment next door, but she declared the prior supervisor's decision "final." If Echenhofer wanted his ticket dismissed, he'd have to argue for it in a scheduled hearing like any other driver.

"I'll have to take time off from work, because of a ticket that never should have been written," said Echenhofer, when he called the Daily News for help.

I spoke with PPA spokeswoman Linda Miller on Echenhofer's behalf.

And - poof! - his ticket was dismissed.

Which raises the question: If the PPA could dismiss a ticket within hours of a newspaper columnist laying out the very reasonable facts of Echenhofer's case, why the hell couldn't the powermongers at 8th and Filbert do the same for Echenhofer himself?

I'll tell you why. Because no one at the PPA cared enough to use his enormous power for good, the way he could have.

Now the PPA will tell you that its protocols are meant to keep the ticket-writing process on the up-and-up, and that's why the initial PPA officer wrote the ticket. And why the initial supervisor got shot down. And why the next supervisor didn't go out of her way for Echenhofer. And why the clerk at the bureau of adjustment refused to let Echenhofer talk with a higher-up.

But that's B.S. If Miller could see the reasonableness of Echenhofer's case, others could have, too.

They just didn't want to.

"It's one thing to be incompetent," which would've been bad enough, said Echenhofer. "But these people were proactive in their contempt."

Echenhofer deserves an apology from the PPA, along with a pat on the back for being the kind of citizen who will stop to help a person in need.

We should reward people like that, not punish them.

Email polaner@phillynews.com or call 215-854-2217. For recent columns: www.philly.com/Ronnie. Read Ronnie's blog at www.philly.com/RonnieBlog.