Compare the trip, not the empty seat
How do occupancy and whole-vehicle trips change an energy comparison?
Entering midway? Revisit Less pollution added does not mean none remains for the preceding worked example, or start here and use the explanation below.
Start with a concrete question
Original synthetic scenario. A fictional car uses 2 energy units per distance unit; a bus uses 10. All travelers must be transported and each vehicle travels the full distance.
Try the initial inputs, then write a prediction before changing one setting. All calculations run locally on your CPU.
What do you expect?
Will a bus always use less energy per traveler, even for a very small group?
Change one thing. Inspect what happens.
- Compare one traveler with thirty while keeping distance fixed.
- Increase car occupancy and observe whole-vehicle rounding.
- Compare traveler counts exactly at and one above bus capacity.
- Write an energy comparison with the same service requirement, then name omitted access and scheduling constraints.
Your settingsMechanism
Calculation belowEvidence
Compare outcomes
Compare the current results
Every bar starts at zero and uses the same numeric scale in this chart. The upper bound automatically adjusts to the largest current value (at least 1), so compare the numbers when changing inputs. Units and quantities come from each label; different kinds of quantity are not interchangeable. Displayed values are rounded to at most six significant digits.Follow the calculation
- Cars needed = ceiling(30 / 1) = 30; buses = ceiling(30 / 30) = 1.
- Assumed car use = 2 energy units per vehicle-distance unit; total = 30 × 10 × 2 = 600.
- Assumed bus use = 10 per vehicle-distance unit; total = 1 × 10 × 10 = 100.
- Divide total energy by 30 actual travelers, not available seats. Empty seats still travel.
Per-person efficiency depends on occupancy and whole-vehicle trip counts. Crossing a capacity boundary can require another vehicle and change the comparison abruptly.
Captures keep your inputs, prediction and observation. Results are recalculated from those inputs. Resetting inputs keeps your captures and challenge history.
Explain the mechanism
What the experiment explains
Original synthetic scenario. A fictional car uses 2 energy units per distance unit; a bus uses 10. All travelers must be transported and each vehicle travels the full distance.
Vehicle energy and energy per traveler answer different questions. Divide by actual passengers and count the vehicles needed to serve everyone.
At defaults, thirty single-occupancy cars use 30×10×2=600 units; one bus uses 1×10×10=100 units. For one traveler, one car uses 20 and one bus uses 100.
Whole-vehicle capacity creates jumps: a 31st traveler with capacity 30 requires a second bus under the stated all-at-once service rule.
Read the relationship
Vehicle count = ceiling(travelers / occupancy). Total energy = count × distance × energy rate. Per-traveler energy = total / travelers.
Inspect the evidence
The numerical trace is recalculated from your current settings. Compare a controlled pair of trials before changing several inputs together. Inspect intermediate quantities as well as final metrics; state which assumptions make the comparison meaningful.
Boundaries of the model
- Invented constant rates; no empirical transport or emissions claim.
- No return trips, route detours, waiting time, accessibility, manufacturing or infrastructure impacts.
Return to the environment and sustainability course and project to connect this mechanism to the broader investigation.
Try a fresh case
Twelve travelers use cars carrying at most 3 each. Each car uses 2 energy units per km over 5 km. What is total energy?
This is a public practice check. Retries support learning; matching a number does not certify independent proficiency.
Take the investigation further
Choose any extension. These are project prompts for you to carry out; they are not automatically assessed.
School investigation
Compare class-trip options with equal traveler counts and explicit assumptions.
College investigation
Add return trips and occupancy distributions, then quantify sensitivity.
Workplace investigation
Draft a travel-policy comparison including access, trip demand and evidence needed to replace synthetic rates.
Keep the evidence, choose your next step
Completion records your own decision that you have worked through this investigation. Practice checks and independent project evidence are separate.