I have a Toyota Corolla.
The driver side door opens from inside even when the door is locked. The door doesn't open when opened from outside.
Is it normal? The only possible explanation that I can think of is that maybe it's designed this way so that driver can open the door even when other doors are locked.
Many car doors are designed to open from the inside when locked so that the occupants can escape the car in an emergency, it's totally normal, although not all cars have that feature. In a car fire you don't want to have to fumble for the lock in order to get out.
How this works is different for many manufacturers, and between cars. On my current mercedes If the car's in park and you open a door all the doors unlock automatically, on my mothers 67 merc 280s with manual locks you have to pull the handle twice, the first time pops the lock, the second time opens the door. On some cars pulling the handle does nothing at all, you have to unlock it manually, on newer cars like that the mechanism is often next to the door handle, on older cars this may mean you need to reach back to pull up the lock post. There's a lot of variation, it's worth thinking about when you get in an unfamiliar car so you know how to get out in an emergency.
Some cars have child safety locks in the back doors, often a switch below the door latching mechanism. This prevents the doors from being opened from the inside in all circumstances. The only way to open the doors is from the outside. I like to try the doors when I get in the back seat of an unfamiliar car just to make sure they aren't activated, I like to control my own destiny.
You'll find that most driver's doors can be unlocked/opened from the inside by pulling the handle without first unlocking them. This is due to the driver's assumed competence in deciding when it is a proper time to open the door.
In contrast, the rear doors do not typically unlock when the handle is pulled due to the likelihood that children occupy those seats and may open the door at an inopportune time. Additionally, many vehicles offer additional protection to where the inner door handle will not open the door even if it's unlocked via a small 'switch' located on the rear doors.
My Fiat 500 and Nissan Qashqai both open from the inside with no need to unlock the doors, unless child lock is activated on that door. How old is your Corolla ? I don't remember seeing this on newer cars
I suppose it's designed under the assumption that locking is meant to stop people from getting into the car (thieves and other unwanted hitchhikers) and it should be easy to get out, not just because of safety issues but also for convenience.
It depends on the manufacturer.
As stated by @GdD this is an explicit safety provision for cases of crashes. Note emphasis.
It is worth to note that modern Volkswagen cars (I can confirm Golf and Passat >=2014) implement SAFE lock, which blocks the handle when the anti-theft is armed. Despite the name, this one is a security (emphasis again) provision that makes it harder for a thief to open a parked car from the outside after breaking the glass.
The two locks engage in different lock modes. When the car is moving, doors are normally locked from the outside but it's still possible to break the glass and open the handle: this is especially true for rescue personnel when passengers are found incapacitated.
On the contrary, when the car is parked and antitheft system is armed, you don't see any possible urgent need for anybody to crack open your car. You actually want nobody to crack it open with the handle when safely parked.
I was also both victim and witness of a very simple car stereo theft where the son of a £$%&/(/%$£"() broke the glass and released the lock of all the cars with ease.
