Baltimore County traffic control signals (aka, traffic lights): They lack intelligence, especially it seems in the White Marsh area. For several months the light at the intersection of Campbell Blvd and Town Center Dr would give priority to vehicles coming from Town Center Dr even at 6am in the morning. It was very apparent that at that time of the morning almost all traffic moved on Campbell Blvd between Route 7 and Honeygo Blvd. Hardly anyone was coming on to Campbell Blvd from Town Center Dr.
In this day and age, you would think that motion detection would be common place, but I've been at a few intersections along my commute where no traffic was moving from any direction. Why is that? It would seem for efficiency's sake that if no motion is detected within a prescribed time frame, it should be ok to give those waiting on the light the green. Instead, we are kept enslaved by simple non-intelligent timers.
Traffic Control Signal Sensors: These are the duel rectangle sensors found embedded in the road at some traffic control signals. These things are good when they work, but it seems that they don't work a good deal of the time.
One morning during my commute to work, a motorcyclist wanted to leave from the police station at White Marsh Mall on Perry Hall Blvd. The rider pushed his motocycle back and forth across the sensor and it wouldn't change the light so that he could make a left-hand turn. Finally, he gave up and turned right instead. Within the next day or so this sensor was fixed to where even I could set it off with my bicycle. This lasted about three weeks before (it seemed) I could no longer trip the sensor. By the way, when a bike does get detected by this sensor, you better not fool around getting through the intersection. From a dead stop, there is only time for a single cyclist to get through the intersection before it goes back to amber. There's not even enough time to clip into my pedal. Similarly, at the lights at the intersection of Honeygo Blvd and Campbell Blvd and at the intersection of Lasalle Rd and Joppa Rd.
Bicycle wheels may be part of the problem. I have had more success with alloy wheels. My carbon wheels will not set off the sensors at all.
Temperature seems to affect these sensors, too.
Ninjas: These are bicyclists and joggers who think that being invisible makes them invincible. These folks are in desperate need of lights, or at the very least something reflective. Ninjas, you FAIL. Some of us do see you, but it's the vehicle operator that doesn't see you that you should be worried about.
Turn Indicators: When did it become unfashionable to use one's turn signal? I would estimate that about 90 percent of the folks in motor vehicles that I meet on the road to and from work do not use a turn signal. So, I'm left wondering as I approach intersections or driveways, is this the guy who's going to right-cross me? Left-cross me?
Too impatient to get in the longer line of vehicles, so let's get behind the shorter line of cyclists: I had this happen the other morning going to work. Some guy in a pick-up truck got behind me at the intersection of Taylor Ave and Perring Pkwy where there's road construction in progress. I'm in a lane that has to merge left after the intersection. To my left is a line of cars maybe three deep. The light turns green; I slowly move forward up to where the road is elevated by 1.5 to 2 inches so that I can get up the elevated section without damaging my bike. The line of cars to my left are doing the same, but assuredly faster than me. The guy in the pickup charges up behind me as if to strike me with his vehicle and after all of the cars to the left go by he roars past my left within two feet of me in frustration.
Traffic calming speed bump: They don't work. People are flying over these newer speed bumps as if they don't care whether their vehicle bottoms out or not.
Road Furniture: While watching the past couple years of the Tour de France the commentators mentioned that the Europeans where slowly getting rid of them because they seemed to cause more accidents then they're suppose to stop. So, what do we do in the good ol' U S of A? We start installing them to calm traffic. There was one just before Morven Rd on Kings Ridge Rd. It lasted no more than a month before someone had an accident on it and it was removed.
-- I plan to continue adding to this list, but if anyone else has something on-topic to add, feel free --