Yes, it is possible for two things to be traveling at the same speed without being noticed by either party, depending on the circumstances and the relative motion between them.
If two objects are moving parallel to each other at the same speed, with no visual cues or reference points to indicate their motion, it can be difficult for either party to notice the relative motion. This is known as "co-moving" or "co-relative" motion, where the two objects maintain a constant distance and velocity relative to each other.
For example, imagine two cars traveling on a straight highway at the same speed, side by side, with no external objects nearby. If both drivers are looking straight ahead and focusing on the road, they may not be aware of the relative motion between their vehicles. From their perspectives, it would seem as if they are stationary and the other car is stationary as well.
However, if there are external reference points, such as landmarks or other moving objects, it becomes easier to detect relative motion. In the case of the cars, if they pass by trees, buildings, or other cars traveling in different directions, they may notice the difference in motion and realize that they are moving relative to each other.
It's important to note that even if two objects are traveling at the same speed, other factors such as wind, sound, or vibrations may still give some indication of their relative motion. But in purely visual terms, under specific conditions, it is possible for two things to be traveling at the same speed without being noticed by either party.