Previously to get data from Toll Plaza you have to approach the concerned agency maintaining the toll. You can request them stating why you need the data and how it will be beneficial. Like during a project work I requested Ashoka Buildcon who was responsible for toll collection on NH 6 Dhulagarh in 2015. However, now India government maintains a online portal with Toll Plaza information. http://tis.nhai.gov.in/index?language=en#
You can take a look of the website. You can get a user manual of how to use the website under the USER RESOURCES head.
I agree with Sudipa, the toll authority should have that data, although they may ask you for project information and for you to come in and meet with them.
These days, camera deployment are common; in my younger days, I had to perform manual counts for each lane from overhead canopy.