Last night I was two cars behind a car that’s brake lights were coming on every two to three seconds. Literally that often, I counted. This went on for the entire time I was behind him/her - close to 15 miles. Could there be something wrong with the car to make this happen, or was the driver really hitting their brakes every couple of seconds?
left-foot braker resting his/her foot on the pedal. see it all the time.
invariably they complain about having to have a brake job done every 8,000 miles.
edit: it’s possible there was something broken inside the brake light switch attached to the pedal, though they’re normally-open switches and typical failure means the brake lights don’t work.
Yep, people driving with both feet, one on the gas and one on the brake. I see it often too. There is no way that they are moving their right foot back and forth from the gas to brake pedals that often.
Sir, after extensive diagnostics the technician has identified the problem with your car. It’s between the driver’s seat and the steering wheel.
To be precise, it’s a loose nut behind the wheel. 
Some automakers (Dodge) occasionally design two wire circuits in such a way that the component is always hot, with the negative leg switched. This kind of nonsense can cause what the OP described when a negative short to earth occurs.
Once when I was young and poor, my taillights were out. I knew what the problem was, but it was about a week before I could fix it. I avoided driving at night, and this was long enough ago that I didn’t have any lights on during the day.
There was one time when I got caught in dimming light on my way home, though, and so I had to turn my lights on. I knew I didn’t have taillights, so I kept tapping the brake with my left foot to make the brake lights come on. I had a manual transmission, so it was quite a trick. I did it for just a few minutes, then I was home.
Made sure I wasn’t out after dark again until I got the problem fixed. It was just a short in a place that was really hard to get to, that was causing the fuses to blow (including a slo-blow fuse), but it was in a place where some paneling needed to come off, and there were some frozen, stripped screws, so I had to take it some place where they could heat them up. It only cost $50, but I was REALLY poor at the time.
Intermitant lights are a problem on all cars. Sometimes it’s your problem, sometime it’s their problem. I’ve solved lots of tail lite problems by making up a real ground wire from the tail lite assembly to the chasis ground. Dont rely on screws or rivets to give a good ground.
On the other hand, don’t discount stupidity.
Case in point. Small town I lived in at the time had a police force looking for crime. Old time cops and new cops recruited by the LA cop cum police chief looking for crimes.
The setup .
Pulled up to thisintersection at 10 - 15 mph. This road takes you through a city park marked at 25mph and everyone in town knows it. You don’t speed through the park. I pulled up to the T intersection from the north and stopped behind 3 or 4 vehicles in front of me. The cop has been behind me for more than half a mile through the park, I know he’s there, no biggie, I’m doing 25 and so are the cars in front of me. No sweat. As soon as we get the the stop signal he lights me up. I pull over. I’m driving a 63 Ford pickup, 220 something straight 6, 3 speed, no granny, no overdrive, short wide box, pickup truck. The dreaded previous owner has installed some really awful orange shag carpet on the roof and floor in an attempt to insulate it from noise and cold. I hadn’t gotten around to taking it out. So Officer Fife asks me for the the usual paperwork and then TELLS me he suspects me of having an illegal brake light cut out switch. ??
I don’t know what he’s talking about and I tell him so. Apparently, in Los Angeles, this is common and he’s not going to let it become a problem in Bumfuck, Oregon.
I don’t know what the hell he’s on about and tell him so. He insists i have this illegal device and proceeds to cheek my rig for it. He even called for backup. Old timer shows up and asks ME what’s up. I tell him to ask the new guy. Barney says I have a secret switch to cut out my brake lights. Old Guy asks “Why would he have one?” “To fool cops” says Barney. “Fool them for what?” says Old Guy. "Nobody runs moonshine or drugs on gravel roads around here like ‘Thunder Road’ says Old Guy.
I’ve never seen cops argue a point of law before so I’m really fascinated. At this point it’s like I’m not even involved in the situation any longer.
Then Barney asks the Old Guy to watch while he pressed my brke pedal and let him know when my brke lights come on. Old Guy says “OK” and stands behing my truck. Fife pushes pedal and waits. No Comment from OG. “AHA” says Fife. “Is the ignition switch on?” asks OG. No apology, “Now it is” says Fife. Pushes brake pedal and Lites on. “On” says OG. About that time the cop radio made noise and OG says “I have to go”.
Officer Fife spends several more minutes trying to find my non-existent cut out switch and tells me “Get out of here, I’ll be watching you.”
Moral of this story; There’s a lot of dumb asses wearing cop suits and too few good cops.
mattm - Trying to decide if you’re a minority and he needed an excuse for why he pulled you over after the fact, or he really is that stupid.
Either way I’m appalled.
Any idea what kind of car it was? On some (all?) electric cars the brake lights come on when you lift off the accelerator and the regenerative braking kicks in.
(bolding mine)
Buuuuttt… you don’t need the ignition switch on for the brake lights to light. Lock `im up, Barney ! 
to the OP: Yes, dude was probably resting his foot on the brake pedal.