Road rage - a car accident

Today morning while going to my work place, while going over a rail over bridge, I saw a car that hit a truck on its rear side, possibly in the darkness. No idea about injuries. Yesterday, same time, I saw the truck at the same place in halt condition, due to some breakdown. The surrounding area was isolated by keeping some tree branches.
Normally, when some vehicle is under breakdown, the driver uses blinkers that are ON indicating about vehicle presence. Some keep stones upto some distance. Some use night reflectors to indicate presence of vehicle.
Nobody expects, vehicle parking on the rail over bridges, flyovers, etc and drive vehicle at full speed, particularly at night times due to little traffic. I suspect accident might have occurred for this reason.
Many times, I too had heart jump while driving on flyovers, as suddenly I find some one talking on mobile after taking sides to the extreme end; some repairing their vehicle; some stopping the vehicle and looking at the nature; and so on.
Some trucks while carrying lengthy rods, pipes, etc do not tie the red flags, do not switch on the blinkers, and those driving behind, if they do not recognize, surely they get involved in accidents.
Road safety is very important for every one and loosing concentration even for a second may lead to deaths.
Sometime back, a person driving his 2-wheeler on a main road died, as all of sudden a mini truck entered from side road to main road rashly, leaving little chance for the person to escape.
I feel there should be speed breakers on all branch roads just before joining the main road so that vehicle speed will come down drastically.
Some places, I found branch roads immediately at the end of the flyovers. This condition too can lead to accidents as those driving fast on flyovers will find vehicles entering from branch roads. This is my personal experience too. Once, I was driving my vehicle on a rail over over bridge. I saw a 2-wheeler raider in front of me skidded and fell down while applying brakes as he saw a vehicle entering from branch road. Seeing this another vehicle driver nearby also applied brakes and he too fell down. From then on, whenever I drive down on flyovers, I am going very slowly, though I drive at speed while driving up on the flyover.