There is essentially no restriction on using brake lights and turn signals at the same time, as they both signal actions/intentions that are often used in conjunction with one another. The brake light signals that you are using your brakes and slowing down, and the turn signal shows your intention to turn. As you will usually slow down as you come up to a turn, there will be many situations where both signals will be on at the same time.
Brake lights and tail lights. (Unless you have a spotter telling you of course)
You do not need the key in the ignition to make lights work. They are "hot" all the time. The reason you Sid marker lights are coming on at the same time is because you have a bad ground in one of your brake lights. It's allowing electricity to jump from the brake lights to the tail light circuit. Take the brake lights apart, clean up all the rust and make sure they "ground" to bare metal. Problem cured.
When both of the turn signals (indicators) of a car blink simultaneously, it is usually because the hazard lights are turned on.
If you have the same bulb for brake and signal, brake light power needs to be interrupted by the signal lights, The brake circuit has to go through the signal light switch so the problem could be there.
Brake lights are on continuously while you are driving. Every time the brake pedal is depressed.
a fuse or fulty wiring the brake lights are useually out the same time as the dash lights if that helps any
Before you take the Chevy in for a diagnostic test, you can look at the fuse box and see if the fuse is burnt for the brake lights. If so, go to some place like AutoZone or O'Reilly's and sometimes someone there will even help you find and replace a fuse. Also, it would be odd if both brake light bulbs burned out at the same time, but not impossible. \
Probably the alternator. Have it checked if it is charging.
Almost all cars use a bulb with two element in it. One for the tail light and one for the brake. It's rare for them to both burn out at the same time.
9 times out of 10, it's just a fuse, check your fuses be sure non are blown out, It has to have blown out for a reason, find any loose grounds, touching wires or wire damage.
The first thing that I would do is look at the arm of the brake pedal and make sure the arm is pressing against the brake switch, press the brake pedal with your hand and see if the switch head goes in. Also if you have someone with you have them watch the brake lights and use 2 fingers and press the head of the switch in and ask if the brake lights are on,it may be that the switch is bad. this would be step 1. depending on how old the vehicle is you may have a broken 12 volt wire or a ground wire, if your turn signals work and your taillights work I would first check the brake light switch. i have never seen 2 brake light bulbs go bad at the same time.
This sounds more like a brake light switch than a bulb. The switch is mounted on a bracket right behind your brake petal.....an inexpensive replacement. If the lights work for a good long time after replacing both at the same time it could be a wiring issue that occurs intermittently. You should replace both brake light bulbs at the same time anyway.....safety first and all.