When a car is travelling in a circular motion or around a bend, the velocity vector is changing constantly. Constant speed means the magnitude of the velocity is unchanging, but the direction is changing. An object in circular motion is therefore simultaneously moving at a constant speed and accelerating.

The acceleration can be resolved into two components with respect to a set of tangential and normal axes:

$$a_c=v^2/r$$ (in the direction perpendicular to the velocity)

$$a_t=\frac{dv}{dt}$$ (In the direction of motion)

If the speed of the car is constant, then: $$a_t=\frac{dv}{dt}=0$$ and $$a=a_c=v^2/r$$

Therefore the car is accelerating towards the centre of the circular motion even though its speed is constant.