The most popular approach is to assume a speed value (free flow speed) for all links or streets joining different origin (O) and destination (D) points and then compute travel time for each link as the ratio of length/speed and finally sum up the travel times on all possible paths between each OD pair. Then choose the path that has the shortest time value. I believe VISSIM should have an in built tool to generate shortest path matrix that is nothing but travel time between all possible OD pairs.

Are you talking about real world measurements to calibrate the simulation?

If so, there are several methods:

1. you could have some probe vehicles driving along the stretches equipped with GPS trackers. They should flow with the traffic. Then you can extract time stamps for the start end end of the stretches for which you want to know the travel time. However, this is a big effort if you need reliable sample sizes.

2. you need to detect and identify vehicles at two points.

2a. In lane-orented traffic you could use automated number plate recognition systems, which are kind of a standard for that. They are realtively expensive and I doubt that they work well in mixed traffic. But you need not detect all vehicles, a little share (a few percent) of the vehicles is enough to get a good estimate of travel times. In some countries you might have issues with privacy when recording number plates.

2b. Instead of video to record number plates, bluetooth signals can be detected. This allows as well to re-identify vehicles. Look e.g. at https://www.youtube.com/watch?v=v2tWSNr8B5I

2c. If you do not have technical equipment, use some students to manually identify the same vehicles at two points where you record the traffic flow on video.

Thanks for your answer and yes iam talking about real world measurements...

Tag on vehicle during peak hour on urban route. It is giving actual TT in mixed traffic . Min 50 vehicles of 2w 4w 3w should be measured and average TT should be considered.one can have handmade big size tag of fast florocent colour which can be fix near highest point of the vehicle which is easily visible .