I'm no expert but I think the speed of the car is somewhat related to the Road Surface Profile. If the car stops travelling, then the road surface stop affecting the suspension system.
If the circled block describes the Road Surface Profile, then the speed should be injected from here.
Thankyou sir I got it from your explanation. its really helpful for me. if we want to make a sinwave at vehicle speed of 20KMPH how to make it then. In simulink i have attached sin wave photo
You are welcome, @Vikas. I'm glad that it is helpful. If you are happy with the proposed solution, please consider accepting ✔ and voting 👍 the Answer. Thanks a bunch! 🙏