There are two doctoral programs at the Harvard Graduate School of Design: Doctor of Philosophy (PhD) and Doctor of Design (DDes).
Prospective students can learn more about the PhD program and see a list of associated faculty here. I am not listed as associated faculty, meaning I am not eligible to serve as an advisor to PhD students, and that I am generally not involved in the PhD program.
Prospective students can learn more about the DDes program here. I can serve as an advisor to DDes students. Students can find instructions on how to apply to the program here. As part of your application, you will need to submit a research proposal that will form the basis of your dissertation/thesis. Although I am not on the admissions committee for the DDes program, I am occasionally asked to review an application from a student who has proposed a research project related to transportation, and to indicate whether I would be willing to serve as that student's advisor (if they were to be admitted). That is the full extent of my involvement in the DDes admissions process. If you are preparing a research proposal as part of your application to the DDes program, I am happy to chat with you about your proposed topic. If that would be helpful, you should sign up for my office hours here.
Prospective DDes students should be aware that admitted students are typically awarded finacial aid that covers part, but not all, of their tuition. I encourage students to carefully consider how they would fund their studies in the DDes program.
Prospective DDes students can find bios of current DDes students here. As you consider whether the DDes program would be a good fit for your your interests and goals, you may find it helpful to reach out to current students to talk about their experience in the program.