It's obvious that you may need to call a tow truck when your car has literally broken down and it won't start, or has suddenly screeched to a halt for some reason. However, there are other times when you should have the car towed rather than driving the car or trying to fix sudden problems on your own. Note a few of those times here so you know you're always safe on the road and don't cause small mechanical issues with the car to get worse over time.
Car suddenly slides while braking
When you apply the brakes, the pads should firmly grip the rotors of the tyres, and the wheels should come to a slow and steady stop. If the car suddenly slides, this often means the wheels are severely misaligned, one tyre has worn down almost completely so there is no tread to grip the road, or one brake pad is gripping the rotors of that tyre too firmly. Whatever the cause, this can be dangerous when driving; not being able to keep your car on the road and under control when braking can easily cause an accident. Have the car towed and repaired and especially before you continue to drive in stop-and-go traffic or on the highway, where safe braking becomes even more essential.
If your car suddenly shuts down and you hear a clicking sound when you try to start it, even if you do get the vehicle started again, you don't want to drive it. That clicking usually indicates an electrical issue; the car could easily shut down again, as the car's computer and many of its other components run on electrical power. Once certain connections or wires are completely worn or frayed, the car may shut down again and you won't be able to start it, so have it towed to avoid this risk.
If the steering of the vehicle suddenly seems very stiff, don't drive the car even if you think you can control it. This steering problem often means there is a lack of steering fluid, or the car's tie rods, which connect the wheels to the axles, could be bent or broken. In these cases, trying to control the steering will only get more difficult as you drive. The same is true if the steering is suddenly very loose, meaning you need to turn the wheel far too much before the car responds. These issues can make it very unsafe to be on the road, so have the car towed instead.