GreenNet Optisim

Diesel to Electric Bus Fleet Simulation

Case Studies

Decarbonisation Feasibility for Zion National Park Bus Fleet

Background

Zion National Park in Utah, USA, operates a high-frequency shuttle service throughout its canyon areas using a fleet of buses that previously ran on diesel. The U.S. National Park Service replaced these diesel buses with battery electric vehicles (BEVs) to meet sustainability goals, reduce emissions, and minimize operating costs.

This case study looks at how the GreenNet team developed a basic energy and logistical model that could have formed the basis for a feasibility study.

Using GreenNet OptiSim, we were able to simulate a full diesel-to-electric transition, model the route with geographic and elevation data, evaluate energy demands, and optimize system performance — all in a matter of hours!

The Problem

The park’s shuttle system:

  • Operates buses every 5–15 minutes from early morning to evening

  • Covers challenging terrain with varying grades and frequent stops

  • Faces constraints such as limited charging locations and the need for high reliability

To make informed decisions, we need to be able to:

  • Accurately model diesel and electric bus performance

  • Determine optimal battery size and charging strategies

  • Forecast operational and environmental impacts

The Solution & Method

Using GreenNet OptiSim, the team developed a detailed digital model of the shuttle system:

Network and Route Modeling

  • Mapped the exact road routes through Zion Canyon, including elevation data

  • Integrated key stops like the Visitor Center, Museum, and Temple of Sinawava

  • Modeled vehicle behavior at stops, loops, and intersections

Vehicle Simulation

  • Created both electric and diesel bus models using real-world performance specs

  • Configured torque curves, battery capacity, weight, gear ratios, and charging needs

  • Simulated energy usage and battery depletion across varying terrain and schedules

Operational Logic

  • Scheduled realistic bus release intervals, passenger pickup/dropoff, and end-of-day charging routines

  • Factored in randomness for stop times and passenger loads to reflect actual operations

Metrics and Analysis

  • Measured key KPIs: diesel cost, emissions, passenger counts, and grid demand

  • Simulated multi-day operations with hourly tracking for each metric

  • Used optimization to determine the minimum viable battery size (500 kWh) to avoid route failures

Impact and Benefits

✅ Feasibility in Hours, Not Months
What once required weeks of planning and assumptions was now modeled in hours using accurate spatial and operational data.

✅ Clear ROI and Emissions Insights
Quantified the emissions reduction and operating cost savings of electrification, supporting grant applications and stakeholder decisions.

✅ Scalable for Other Parks and Cities
The simulation approach used for Zion is transferable to other transport networks considering fleet electrification or carbon reduction strategies.

Conclusion

This case study showcases how GreenNet OptiSim empowers organizations to make informed, data-driven decisions for sustainable transport transitions. Whether you’re a national park, city transit authority, or industrial fleet operator, GreenNet provides the tools to design, validate, and optimize your path to decarbonization.