Guest Blog: The Yellow Light Project


Today’s blog is from a colleague of mine, Heather Buskirk.  Heather teaches Physics and coaches teachers regarding Project Based Learning in upstate New York.  She and I have been collaborating on PBL training for the last several years, and as  you will see, she is a rather thoughtful practitioner.  You should consider her reflection at the end to be an invitation to brainstorm if you have any thoughts on her project for next year.

About a year ago, Kevin blogged a project idea about teaching kinematics through a automobile-themed project here.  Not one to pass on a great idea, I stole it and began designing a project around the question “What do you do at a yellow light?”  Since Kevin is not teaching physics these days though, he left figuring out all the details as an exercise for the reader.

First, a little context about my classroom.  I teach in a program for seniors called the Learning Project, which integrates conceptual physics, math, English language arts, government, and economics.  We meet daily for the first four periods (about three hours) and engage in wall-to-wall project based learning.  I serve at the science and math teacher and a colleague is responsible for the humanities courses.  Students spend the remainder of their school day taking classes back in our traditional high school or vocational technology center.  The students in the program cover the spectrum of achievement (from traditionally successful to struggling) but all share a desire for a different experience in their senior year.  

So while Kevin had given some inspiration about the physics in his blog, we had to find a way to bring in all our other courses as well.  We decided to have the students explore some structures of local government and the economics of auto insurance.  The project culminated with the students presenting to a panel including a representative of County Board of Supervisors Public Safety Committee, a local sheriff, and a local auto-insurance agent.  You can see our entry doc here.

We launched the project with a class discussion about how you should behave at a yellow light versus how people actually do.  The discussion was fairly rich and inspired great opportunities for some in the field data collection.  The sheriff gave us a list of the most problematic intersections near the school, which we then divided up and assigned to the student groups.  While formally, they had to just time the yellow lights and note speed limits for each approach to the intersection, by spending so much time at the intersections the students noted much more.  Every group returned with stories of watching in disbelief how many people blatantly ran the red light and several reported seeing close calls almost becoming accidents.  The field research fired the students up even more than I had anticipated and provided ample motivation to dig deeper into the physics of motion.

Our math course for the Learning Project is a senior elective called the Mathematics of Science, which allows ample opportunities for exploring the intersection of physics and math.  With this project, I wanted to review graphing functions (linear and quadratic) and do a bit with piecewise functions.  While my students come to me with math readiness varying from still struggling with Algebra to taking Calculus concurrently, I have no easy task when trying to support and challenge all of my learners.  I do find however that all of my students can benefit from a bit more practice with graphing.  In kinematics, the graphing can both serve as an access point for students who struggle with algebraic manipulations and as a entry into calculus.  In addition, all students were new to graphing and making sense of their own data and using online graphing tools.


We began by creating a storyboard for a car approaching and stopping at a yellow light.  From the storyboards, the students broke up the motion into pieces and then completed some quick investigations using toy cars and motion detectors to get the shapes of the motion graphs for each piece.  We then connected them to our kinematic equations and substituted in the real world values for reaction time, speed, and acceleration while braking.  

Student work - yellow light

This group’s analysis is broken into the reaction time for noticing the yellow light and applying the brake in purple, the time braking in green, and then the car at rest at the intersection.  With the final graph here the students figured out the car would travel nearly 30 meters before coming to rest given their data and assumptions.  Based on their analysis, these students then proposed the addition of signs at this distance from the intersection which would clue cars to stop if the light has turned yellow.  When the project was presented though, the analysis got a bit lost and jumbled.

In the end it turns out this project had a lot of pieces and they all did not fit together as seamlessly for my students as I had envisioned.  The tie in with Newton’s Laws was pretty forced and the students felt overwhelmed by the variety of panelists they had to address.  The analysis turned out to be pretty involved even with some fairly liberal assumptions (such as treating braking as a constant acceleration).  

So as I am turning my focus to the upcoming new year, I am seriously reconsidering my treatment of this project.  While the premise is strong, I think we need to focus the final product a bit more and tighten up the entry doc.  Also, now that I have a better idea of where the students will struggle through the analysis I can re-work my scaffolding plan.  Ultimately, I am wrestling with how can I give my students more agency and leadway in this project, without loosing the juicy physics?  Or alternatively, how can I get into some rigorous analysis without sliding to a super teacher centered approach?