some ideas

1- Traffic Accident Analysis Using Deep learning

2 - Big data analytics for public transportation improvement

3- Intelligent Traffic Congestion management

... good luck

4 - Traffic Operations, Safety $ Human Factors

Autonomous Transportation - very trendy topic.

You may work on :

Sustainable transportation system

Some ideas!

1. Sustainable Transportation

2. Traffic safety

3. Human factors responsible for accidents

---As traffic is one of the main problem faced by all TIER-I

cities,researching on this one using the available tools like Nash

equilibrium will help to find better solution..

---price comparison public/private transport

wish you all the best for your work..thankyou..

Network traffic

An application of Nash equilibria is in determining the expected flow of traffic in a network. Consider the graph on the right. If we assume that there are x "cars" traveling from A to D, what is the expected distribution of traffic in the network?

https://en.wikipedia.org/wiki/Nash_equilibrium

Well, this question is too broad, there are many diversified fields in transporation engineering.

I'd suggest you spend some time to firstly investigate some overal and basic concepts of traffic & transportation engineering quickly. This will help you understand main subjects and areas and research focuses and helps you understand your area of interests as well.

It can be fruitless to pick a very specific topic such as autonomous transporation, before understanding the main subjects. I suggest you do research on this or that topic if this is not really what you'd want to do.

I'd suggest you start even with some wikipedia articles which are very concise and infroamtive (at least when it comes to the overal definitions and problems) some quick examples:

https://en.wikipedia.org/wiki/Traffic_flow

https://en.wikipedia.org/wiki/Fundamental_diagram_of_traffic_flow

https://en.wikipedia.org/wiki/Traffic_simulation

https://en.wikipedia.org/wiki/Microscopic_traffic_flow_model

https://en.wikipedia.org/wiki/Macroscopic_traffic_flow_model

https://en.wikipedia.org/wiki/Road_traffic_safety

https://en.wikipedia.org/wiki/Traffic_psychology

these articles are mainly focused on traffic flow theory and traffic safety which is the area of my interest. I'm sure you can find similar topics on other aspects of transportation engineering. You don't need to study deeply all details mentioned in these articles. These should give you some overal insights to choose your research direction.

I suggest after you've picked your area of interest, just read one or two reveiw paper on that topic, you may even ask again about good review papers in that area and people will advise you. Then you will be in a very better position and I'm sure you'll find some topics to work on.

I hope this helps

Saeed