The Tiramisu v3 app icon. A white T stylized as a transit map on a blue background.

Tiramisu Transit

Three app icons, corresponding to the three versions of Tiramisu. Left: a bus with a clock behind it in brown. Center: same, but with different colors. Right: a white T stylized as a transit map on a blue background.
Tiramisu’s icons for versions V1 (left), V2 (center), and V3 (right).

After 10+ incredible years, we retired the Tiramisu Transit app in the spring of 2022. When we launched this project, we never expected it to grow so large and have so much impact. Our longevity and success come from our loyal app users, research participants, student researchers, and technical staff. We also must thank Port Authority and Pittsburgh’s passionate and thriving transit community!

In 2008, the Rehabilitation Engineering Research Center on Accessible Public Transportation (RERC-APT) at Carnegie Mellon was started to make public transit more inclusive for people of all abilities. The early vision was to help people identify accessibility barriers, report them to the service provider, and then track progress on the removal of those barriers. During a lab study, a participant remarked that this was a great idea, but if the bus was too full for their wheelchair, the problem of barriers was moot. In parallel, participants who are blind noted the lack of real-time arrival information for transit users in Pittsburgh. This led to long waits outdoors in unsafe locations and during inclement weather. In the late 2000’s, such systems were cost-prohibitive for many transit systems to install, including here in Pittsburgh.

Our team observed that the combination of crowdsourcing and smartphones could gather both fullness and arrival time data. We launched an effort to design, build, and deploy a system where users could report fullness and trace transit vehicles while onboard. This became the first version of Tiramisu. Over the years, Pittsburgh users provided over 200,000 crowdsource contributions. After Port Authority rolled out real-time data, we shifted our research to focus on personalized transit information. Version 3 of the app allowed users to filter which information they were shown. The system learned what filters to automatically pre-select, leading to less user effort to get the information they wanted.

Along the way, the project has had a significant impact in both the research community and the broader society. In particular, Tiramisu has been used by about 75,000 unique users in Pittsburgh since 2011. This daily impact occurred in parallel with award-winning interdisciplinary research that has influenced multiple research communities. 

Aside from a long list of peer-reviewed research papers (list below), the team has received recognition through 5 paper awards, an innovation award from a very large professional society on intelligent transportation (ITSA), an innovation award from the Federal government (FCC), and a dissertation award (ACM SIGCHI). 

Tiramisu also provided a great opportunity for many students and postdocs to learn how to conduct research while working on a project with community and accessibility impact. Alumni of the project are listed below.

Three app images of bus arrival times, corresponding to the three versions of Tiramisu. Left: bus routes are filtered out by favorites routes in blue and brown. Center: bus routes are filtered out by nearby stops in dark and light brown. Right: bus routes are filtered out by closest stop and predicted routes (in orange). There's a little icon that indicate whether the route is scheduled or it was fed from the real-time transit system.
Tiramisu’s user interfaces for versions V1 (left), V2 (center), and V3 (right)


Tiramisu Transit could not have been accomplished without all of the people who worked on the project:


Yun Huang
Alex Haig
Oscar J. Romero

Students and staff

Adubor, Obehioye
Ahuja, Sarthak
Ajith, Archana
Amick, Sara
An, Yufei
Andrianoff, Terabyte
Araujo, Kevin
Ayoob, Ellen
Aziz, Rafae
Balaji, Vinay
Barry, Devon
Bing, Zhong Yu
Biswas, Abhijat
Bloomfield, Leslie
Bruggeman, Christian
Bury, Maxime
Callebert, Lucile
Carter, Liz
Chan, Madeline
Chatterjee, Ishani
Chen, Hong
Chen, Stepahnie
Connelly, Joe
Corzo, Yasser Albert
Cunden, Steven
Dave, Shaan
Dehsen, Lauren Von
Deng, Sophia
Ding, Ximin “Teddy”
Doryab, Afsaneh
Elhiraika, Omer
Gao, Jing
Gardiner, Steven
Giampapa, Joseph
Goldman, Jonathan
Goodale, William
Gosalia, Meghal
Gupta, Niloy
Hayati, Shirley Anugrah
He, Xiao “Ivy”
Hiruncharoenvate, Chaya
Hochendoner, Eric

Hong, Chen
Hu, Hanzhang “Echo”
Huan, Ran
Jagannathan, Somakala
Jain, Krati
Jeong, Yujeong
Ji, Rufeng “Steven”
Jin, Yang
John, Rhomni St.
Kaniarasu, Poornima
Kharbanda, Saumya
Kim, Ildoo
Kirabo, Lynn
Kumar, Piyush
Li, Jian
Limprayoon, Jirachaya “Fern”
Liu, Yinjia “Franklin”
Luo, Tewei
Mahalchick, Stephanie M
Maheshwari, Nikita
Malik, M. Zubair
Mason, Erika
McMillan, Julie
Min, Byung Cheol
Min, Jun Ki
Morales, Cecilia
Nagabandi, Anusha
Nanavati, Amal
Nayak, Amukta
Nip, Terence
Odom, William
Olivier, Raphael
Omelchenko, Sofia Gadea
Pan, Tianlei
Pareek, Prithu
Park, Jonathan
Park, Sun Young
Patel, Aakash
Pei, Yuxin “Abbey”
Raack, Taylor
Rajendra, Varsha
Rao, Adithi

Rao, Shree Lakshmi
Rathi, Neha R.
Reig, Sam
Richter, Michael
Ringwalt, Daniel
Rivard, Kathryn
Schweers, Jenny
Seo, Jeong Min
Shankar, Vivek
Shao, Yizhou
Silvera, Gustavo
Smith, Andrew
Smith, Andy
Sun, Bili
Suppe, Arne
Tan, Sarah
Tan, Xiang Zhi
Thiruvengadam, Nikhil Ravi
Traficante, Rosalie
Tran, Allison
Traut, Elizabeth
Urbina, Lynn
Valenti, James
Vázquez, Marynel
Wang, Allan
Wang, Antian
Wang, Clara
Wang, Di
Wang, Jialiang
Wei, Le
Won, Agnes
Wu, Yongzuan
Xing, Yifan
Xing, Yue
Yang, Chenhao
Yang, Qian
Yoo, Daisy
Youn, Kyungmin
Zhang, Tyrone
Zhang, Xiyang
Zheng, Sunny

Faculty Mentors

Charlie Garrod
Aaron Steinfeld
Anthony Tomasic
John Zimmerman

Point of contact

Aaron Steinfeld

"Tiramisu, the real time bus tracker" with a bus and wifi bars in the upper right corner.


Open-source code

We contribute this work to the community by releasing the open-source code of Tiramisu Transit version 3.0 on GitHub.



  1. Romero, O. J., Haig, A., Kirabo, L., Yang, Q., Zimmerman, J., Tomasic, A., & Steinfeld, A. (2020). A Long-Term Evaluation of Adaptive Interface Design for Mobile Transit Information. In 22nd International Conference on Human-Computer Interaction with Mobile Devices and Services (pp. 1–11).


  1. Traut, E. J., & Steinfeld, A. (2019). Identifying commonly used and potentially unsafe transit transfers with crowdsourcing. Transportation Research Part A: Policy and Practice, 122, 99–111.
  2.  Steinfeld, Aaron, Bloomfield, L., Amick, S., Huang, Y., Odom, W., Yang, Q., & Zimmerman, J. (2019). Increasing Access to Transit: Localized Mobile Information. Journal of Urban Technology, 26(3), 45–64.


  1. Pi, X., Qian, Z., Steinfeld, A., & Huang, Y. (2018). Understanding Human Perception of Bus Fullness: An Empirical Study of Crowdsourced Fullness Ratings and Automatic Passenger Count Data. Transportation Research Record, 2672(8), 475–484.


  1. Steinfeld, Aaron, Maisel, J. L., & Steinfeld, E. (2017). Accessible Public Transportation: Designing Service for Riders with Disabilities. Routledge.


  1. Yang, Q., Zimmerman, J., Steinfeld, A., & Tomasic, A. (2016). Planning Adaptive Mobile Experiences When Wireframing. In Proceedings of the 2016 ACM Conference on Designing Interactive Systems (pp. 565–576).
  2. Huang, Y., Zimmerman, J., Tomasic, A., & Steinfeld, A. (2016). Combining contribution interactions to increase coverage in mobile participatory sensing systems. In Proceedings of the 18th International Conference on Human-Computer Interaction with Mobile Devices and Services (pp. 365–376).


  1. Tomasic, A., Zimmerman, J., Garrod, C., Huang, Y., Nip, T., & Steinfeld, A. (2015). The performance of a crowdsourced transportation information system.


  1. Tomasic, A., Zimmerman, J., Steinfeld, A., & Huang, Y. (2014). Motivating contribution in a participatory sensing system via quid-pro-quo. In Proceedings of the 17th ACM conference on Computer supported cooperative work & social computing (pp. 979–988).


  1. Steinfeld, Aaron, Rao, S. L., Tran, A., Zimmerman, J., & Tomasic, A. (2013). Co-producing value through public transit information services. Advances in the Human Side of Service Engineering, 231–40.
  2. Huang, Y., Tomasic, A., An, Y., Garrod, C., & Steinfeld, A. (2013). Energy efficient and accuracy aware (E2A2) location services via crowdsourcing. In Wireless and Mobile Computing, Networking and Communications (WiMob), 2013 IEEE 9th International Conference on (pp. 436–443).
  3. Daisy Yoo, John Zimmerman, and Tad Hirsch. (2013). Probing bus stop for insights on transit co-design. In Proceedings of the SIGCHI Conference on Human Factors in Computing Systems (CHI ’13). Association for Computing Machinery, New York, NY, USA, 409–418.


  1. Zimmerman, J., Tomasic, A., Garrod, C., Yoo, D., Hiruncharoenvate, C., Aziz, R., Steinfeld, A. (2011). Field trial of Tiramisu: crowd-sourcing bus arrival times to spur co-design. In Proceedings of the SIGCHI Conference on Human Factors in Computing Systems (pp. 1677–1686).
  2. Steinfeld, Aaron, Zimmerman, J., Tomasic, A., Yoo, D., & Aziz, R. D. (2011). Mobile transit information from universal design and crowdsourcing. Transportation Research Record, 2217(1), 95–102.


  1. Yoo, D., Zimmerman, J., Steinfeld, A., & Tomasic, A. (2010). Understanding the space for co-design in riders’ interactions with a transit service. In Proceedings of the SIGCHI Conference on Human Factors in Computing Systems (pp. 1797–1806).
  2. Steinfeld, Aaron, Dar Aziz, R., Von Dehsen, L., Park, S. Y., Maisel, J. L., & Steinfeld, E. (2010). The value and acceptance of citizen science to promote transit accessibility. Technology and Disability, 22(1), 73–81.


Pittsburgh stakeholders

None of this work could have been accomplished without valuable input from various local stakeholders. Organizations include the Port Authority of Allegheny County, the Committee for Accessible Transportation (CAT), Blind & Vision Rehabilitation Services of Pittsburgh, and Achieva. In addition to these organizations, we want to highlight Pittsburgh’s passionate and thriving transit community who adopted Tiramisu, provided a steady supply of suggestions and feedback, and found enough value in Tiramisu to use it in their daily life.


Core funding for the Tiramisu project has been through the Rehabilitation Engineering Research Center on Accessible Public Transportation (RERC-APT). The RERC-APT was originally funded by the Department of Education through the National Institute on Disability and Rehabilitation Research (H133E080019 & H133E130004). It is now funded by the National Institute on Disability, Independent Living, and Rehabilitation Research (90RE5011 & 90REGE0007). NIDILRR is a Center within the Administration for Community Living (ACL), Department of Health and Human Services (HHS).

Additional support was provided by US DOT through the T-SET and Mobility21 University Transportation Centers and the ATTRI Program.

Additional support was provided by the Traffic21 Institute at Carnegie Mellon University, a program developed with the support of the Hillman Foundation.

Other lab support was provided by IBM and Google.