STEM Lessons for Pedestrian Safety: Need for Speed?

NHTSA · 2020 · ROSA P / United States. Federal Highway Administration

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Summary

This document presents a structured educational lesson plan titled “Need for Speed?” designed for middle school students to explore the relationship between vehicle speed, human biology, and pedestrian safety. The lesson addresses the critical issue that vehicle speed is a primary factor in roadway safety, emphasizing that higher speeds lead to more severe impacts and that pedestrians are disproportionately injured compared to vehicle occupants. The curriculum aims to demonstrate how street design influences driver behavior and how the physical principles of physics and human reaction times determine the distance required for a driver to stop safely. The instructional design is a 60–75-minute classroom activity involving six distinct parts. It begins with an analysis of street imagery and news stories regarding pedestrian crashes to identify environmental cues that influence driving speed and to discuss factors often omitted in crash reporting. Students then engage in a ruler-drop experiment to measure their individual visual reaction times, distinguishing between reflexes and cognitive response times. Using these measured reaction times, students calculate Stopping Sight Distance (SSD) using the equation $SSD = vt + (v^2/30[a/g])$. They apply this formula to various scenarios involving velocities of 20, 30, 40, and 50 miles per hour and different deceleration rates. Finally, students physically measure and mark these calculated stopping distances in a hallway or outdoor space, allowing them to visualize the spatial requirements for safe stopping. Optional extensions include calculating SSD adjustments for road grades. The lesson provides specific parameters for calculations, including converting miles per hour to feet per second and using standard gravity ($32.2 \text{ ft/s}^2$). Deceleration rates are contextualized by vehicle type and braking urgency, ranging from $2 \text{ ft/s}^2$ for comfortable truck braking to $20 \text{ ft/s}^2$ for urgent passenger vehicle stops. The document notes that transportation safety fields typically assume a standard reaction time of 2 to 2.5 seconds, which students compare against their own measured averages. The physical layout activity requires a space of at least 450 feet to accommodate the longest stopping distances associated with 50 mph scenarios. The significance of this lesson lies in its ability to translate abstract safety concepts into tangible, experiential learning. By measuring their own reaction times and calculating stopping distances, students understand that speed is not merely a legal limit but a physical decision with biological and mechanical consequences. The curriculum highlights that street design can encourage slower speeds, thereby reducing stopping distances and improving pedestrian safety. It also underscores the impact of variables such as impairment, lighting, and road grade on crash severity, reinforcing the importance of comprehensive road design and responsible driving behavior.

Key finding

The educational activity demonstrates that vehicle speed and driver reaction time are critical factors in determining stopping distances, highlighting how street design can influence driver behavior to improve pedestrian safety.

Methodology

other

Provenance

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Topics

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• braking response
• perception reaction time