Micro mobility: Center of Gravity- Height and Risk

The higher the center of gravity (CoG) relative to the vehicle’s stability base, the more likely the vehicle and rider are to become unstable. You can measure this or envision it as a simple triangle, smaller base=less stable.

Scooters and rental bikes are single track vehicles, meaning balance is dynamic and the rider is a key component within a system of moving forces. It stands to reason that all riders are not alike. Design must be flexible. On a two wheeled vehicle the dynamics of stability and the exact placement of CoG are preeminent criteria at design stage.

On a four wheeled vehicle the base and weight are kept low in order to maximize traction or “grip.” Wheels are positioned as far as possible into the “corners” to maintain that base as speed increases and wheels are designed to maintain maximum surface contact under deceleration forces.

We would argue that within the micro mobility rental market, the liability for correct design ergonomics is often placed outside of a fleet business model. There is a fundamentally dangerous dynamic at play when unlicensed riders, with the exuberance of youth, pit their skillset against 2 ton tanks on public roads.

Coupled with minimal intrinsic protection (like what you find in cars; airbags, crumple zones, seat belts, sensor technologies, seating design, frame, inertial damping, suspension systems, ABS, collision mitigation controls, radial tires, turn signals and windshield wipers), the risk of severe injuries, especially to the head, increases significantly.

Key Dynamics at Play:

1. Physics of CoG and Stability:
   • A higher CoG makes it easier for small destabilizing forces (e.g., uneven ground, sharp turns, sudden stops) to tip the rider off balance.
   • The likelihood of ejection grows as the vehicle’s acceleration or deceleration increases, especially when braking from high speed on small diameter wheels.
2. User Height and Ergonomics:
   • Taller riders naturally raise the CoG, exacerbating stability issues.
   • Shorter riders, while lowering the CoG slightly, may face ergonomic challenges like poorly placed handlebars or foot platforms, leading to compensatory postures that increase risk.
3. Impact Risk in Head-First Falls:
   • When riders are ejected from vehicles with high CoG, they tend to fall head-first (pitchpoling) due to forward momentum and body mechanics.
   • The absence of helmets magnifies the likelihood of traumatic brain injury (TBI) upon impact.
4. Demographics and Age:
   • Younger and older riders are more susceptible to injury due to lack of coordination, slower reflexes, or a greater likelihood of improper vehicle use (e.g., “doubling up” on e-scooters).

Recommendations for Design and Policy:

• 🟧 Vehicle Ergonomics and Stability:
  • Lower CoG: Ensure the platform where riders stand is as low to the ground as possible.
• 🟧 Adjustable Features: Incorporate adjustable handlebars to accommodate varying user heights without compromising stability.
  • Wider Bases: Provide wider wheelbases design configurations to enhance stability.
• 🟧 Speed Regulation:
  • Implement stricter speed limits (via geofencing) in areas with high pedestrian traffic or uneven road surfaces.
  • Limit acceleration rates to reduce destabilization during quick starts, stops or turns.
• 🟧 Impact-Absorbing Features:
  • Use handlebar designs that fold inward during a crash to reduce injury.
  • Equip vehicles with small, lightweight airbags or padded surfaces for critical impact zones.
• 🟧 Helmet and Protective Gear Incentives:
  • Develop systems that reward riders for using helmets (e.g., discounts on rides).
  • Design onboard storage for collapsible helmets.
• 🟧 Educational Campaigns:
  • Provide clear signage on vehicles about maximum recommended heights and proper riding posture.
  • Integrate tutorials into rental apps about weight distribution and safe riding techniques and collision avoidance.
  • Good balance is not innate, it is trainable.
• 🟧 Brakes and wheels
  • Within the motorcycle and cycling industry, brakes and wheel sizes are key design constraints.
  • Suspension damping technologies and adaptive braking

Expert Take: Why Design Matters More Than Policy Alone

Policy can mandate speed limits and protective measures, but fundamental issues arise from vehicle design itself. A poorly designed vehicle increases risk regardless of policy. By addressing CoG, stability and rider ergonomics at the design phase, manufacturers can significantly mitigate traumatic head and facial risks.

One of the most easily identifiable contributors to injury severity is the lack of a helmet requirement while operating e-scooters and e-bikes.

anesthesiologynews.com