While biking to work this morning, I saw something happen that’s all too common in Boston: A driver opened her car door into the bike lane without looking. As you might’ve guessed, a biker in front of me, unable to avoid the door in the split second after its opening, slammed into the door, flipped over, and landed very hard on her shoulder.

Now, I had never been close enough to really call myself a witness — maybe just a passerby who saw only the impact, but never enough to see who was at fault. This time, however, I saw it all. And there were a few things I saw that really irked me.

First, the way the driver behaved after the accident was unacceptable. And it really suggests only one thing: an honest lack of understanding of the law regarding motorists’ responsibility to bikers and bike lanes. So, to be clear, this is what the law states, from Chapter 90, Section 14 of the Massachusetts General Laws regarding Motor Vehicles and Aircraft:

No person shall open a door on a motor vehicle unless it is reasonably safe to do so without interfering with the movement of other traffic, including bicyclists and pedestrians.

It’s really that simple. And the police officers who arrived on the scene agreed. The opening of the driver’s door caused the accident. The driver is at fault, which I’m sure will be good news to the victim since she said she's a massage therapist who relies on the use of her hands and arms to make a living — and thus could likely be out of work for a while.

So to the woman who was “doored” on her bike near St. Paul Street and Commonwealth Avenue, rest assured: You are not at fault. I made a statement to the police assuring them that you were not at fault in the slightest.

And that brings me to my next point.

Of the four bikers who saw the accident, only a guy named Will and myself stayed until the ambulance came. Soon after it arrived, however, Will had to leave, admitting he hadn’t seen the accident well enough to feel it would help if he stuck around. Otherwise, not one of the other witnesses stayed to help. In fact, one of them — the biker who rode directly behind the victim when the accident happened — didn’t even get off of his bike before saying, “Which one of you guys is going to take care of her?” Mind you, the woman was still lying in the street, crying, and writhing in pain.

And while his question was bad enough, the silence after the question was even worse. Almost no one bothered to swing their leg over their bike frame and help. Almost no one stayed until the ambulance came and no one else stayed to give a police report.

I understand we live in a city and we’re trying to get from point A to point B with as few obstacles as possible. But there are obstacles and then there are people. People who actually need your help and might be saved a lot of grief if you just stuck around for 15 minutes. As I said, the woman who was hit is a massage therapist. She makes her living on the ability to move her shoulders, arms and hands. If no one had been there to back up the biker, the driver — who tried to leave after suggesting she just leave her name and number — would have taken off without making a statement to the police, stiffing the biker with the cost of an ambulance and other costs incurred as a result of the accident.

I think the lessons learned from this experience are two-fold, and this goes to both motorists and bicyclists alike: Familiarize yourself with Massachusetts law regarding bikes, bike lanes and motorist responsibilities, and for goodness sake don’t avoid doing what’s right just because it’s inconvenient. Be a Good Samaritan when you get the chance. It’s often more important than you think.