It depends on the type of hybrid car you are talking about. In one type of hybrid, there will be a gasoline engine and at least one electric engine capable of driving the wheels. In this case, the gasoline engine must still use a transmission because it cannot be revved too high without causing major damage or shortened life. One possible solution to this transmission issue would be to use a Continuously Variable Transmission (CVT), which can be more expensive but keeps the engine at peak efficiency.

The other type of hybrid, where the wheels are driven entirely by electric motors (and has a gasoline generator to charge the battery) does not require a transmission because electric motors have a very wide range of acceptable RPM. Additionally, electric motors have a relatively flat torque curve and the max torque is available instantly. I should note that this type of "hybrid" car is generally just called an electric car since the gasoline motor is used to charge the battery only and does not drive the wheels.

It depends on the type of hybrid car you are talking about. In one type of hybrid, there will be a gasoline engine and at least one electric engine capable of driving the wheels. In this case, the gasoline engine must still use a transmission because it cannot be revved too high without causing major damage or shortened life. One possible solution to this transmission issue would be to use a Continuously Variable Transmission (CVT), which can be more expensive to manufacture but keeps the engine at peak efficiency.

The other type of hybrid, where the wheels are driven entirely by electric motors (and has a gasoline generator to charge the battery) does not require a transmission because electric motors have a very wide range of acceptable RPM. Additionally, electric motors have a relatively flat torque curve and the max torque is available instantly. I should note that this type of "hybrid" car is generally just called an electric vehicle (EV) since the gasoline motor is used to charge the battery only and does not drive the wheels.

I was going to comment this, but don't have the reputation: The diesel-electric transmission you referred to is more closely related to today's EVs in that a diesel engine charges batteries, which then in turn power electric motors at the wheels. Transmissions in trains are impractical for several reasons (such as need to power up to four axles and the number of gears that would be required to keep it at peak efficiency) and this eliminates the need for a true transmission.