Safety and value

Why this matters

A drone medical delivery service must answer two questions before the hospital director approves it: is it safe enough? and is it worth the money? A drone that delivers quickly but falls onto a roof, or a service several times dearer than a motorcycle courier with no added benefit, will not go ahead.

Safety and permission

Beyond-visual-line-of-sight delivery over communities carries more risk than ordinary flying. JARUS SORA 2.5 is a risk assessment method for operations in the Specific category, which includes delivery. In Thailand, permission must be obtained under the CAAT announcements in force (see UAT 313) and CAB Regulation No. 94, which prohibits dropping or suspending objects without permission (module 1). Within the organisation, a safety management system (SMS) follows ICAO Doc 9859.

No single layer prevents every accident; safety comes from overlapping layers. Routes avoiding communities reduce the consequences of a crash, energy reserve (module 2) reduces the chance of running out of battery, a geofence keeps the drone inside its area, and occurrence reporting lets the system learn from near misses.

Total cost of ownership and break-even

The knowledge unit on life-cycle cost uses: initial cost + years × (annual fixed cost + jobs × cost per job). Options must deliver the same kind of result to be compared. In our case the existing option is paying a motorcycle courier per trip.

YEARS, SETUP, FIXED, DRONE_TRIP, BIKE_TRIP = 5, 1_500_000, 300_000, 60, 250

def drone_cost(trips_per_year):
    return SETUP + YEARS * (FIXED + trips_per_year * DRONE_TRIP)

def bike_cost(trips_per_year):
    return YEARS * trips_per_year * BIKE_TRIP

for n in (1000, 3000, 5000):
    d, b = drone_cost(n), bike_cost(n)
    print(f"{n:>5} trips/yr: drone {d:>10,.0f}  motorcycle {b:>10,.0f}  -> {'drone' if d < b else 'motorcycle'} cheaper")
break_even = (SETUP + YEARS * FIXED) / (YEARS * (BIKE_TRIP - DRONE_TRIP))
print(f"break-even about {break_even:,.0f} trips per year ({break_even / 365:.1f} per day)")

 1000 trips/yr: drone  3,300,000  motorcycle  1,250,000  -> motorcycle cheaper
 3000 trips/yr: drone  3,900,000  motorcycle  3,750,000  -> motorcycle cheaper
 5000 trips/yr: drone  4,500,000  motorcycle  6,250,000  -> drone cheaper
break-even about 3,158 trips per year (8.7 per day)

Present value

Money paid in the future is worth less than money today. NIST’s life-cycle costing manual (Handbook 135) therefore discounts each year’s cost with a discount rate before adding. An option with a large up-front payment is slightly disadvantaged when discounted.

YEARS, SETUP, FIXED, DRONE_TRIP, BIKE_TRIP = 5, 1_500_000, 300_000, 60, 250
RATE, TRIPS = 0.03, 4000

pv_drone = SETUP + sum((FIXED + TRIPS * DRONE_TRIP) / (1 + RATE) ** t for t in range(1, YEARS + 1))
pv_bike = sum(TRIPS * BIKE_TRIP / (1 + RATE) ** t for t in range(1, YEARS + 1))
print(f"{TRIPS} trips/yr, discount {RATE:.0%}: PV drone {pv_drone:,.0f}, PV motorcycle {pv_bike:,.0f}")
print(f"undiscounted: drone {SETUP + YEARS * (FIXED + TRIPS * DRONE_TRIP):,.0f}, "
      f"motorcycle {YEARS * TRIPS * BIKE_TRIP:,.0f}")

4000 trips/yr, discount 3%: PV drone 3,973,042, PV motorcycle 4,579,707
undiscounted: drone 4,200,000, motorcycle 5,000,000

Non-monetary value

Stolaroff and colleagues (2018) found that small drones delivering light packages use less energy and emit less greenhouse gas per package than delivery trucks in most cases, but heavy packages may reverse this, and extra warehouse energy must be included. Environmental benefit therefore depends on the details of the service, and drones should not be claimed as always “greener”. Other effects to assess include shorter delivery times, service continuity during disasters, and community effects such as noise.

Module lab

Common mistakes

Summary

• Safety comes from several layers, and permission follows SORA and CAAT announcements
• Total cost = initial + years × (fixed + trips × cost per trip); drones pay off beyond the break-even point
• Discount costs to present value following NIST Handbook 135
• Assess non-monetary and environmental effects from real data

Check your understanding

1. Initial cost 1,000,000 baht, fixed 200,000 baht a year over 5 years, drone 50 per trip against 200 for the existing option. What is the break-even point in trips per year?
2. What is the present value of 100,000 baht paid in 2 years at a 3% discount rate?
3. Why are future costs discounted?
4. Which category of operations does SORA apply to?
5. Why should drones not be claimed as always more energy-efficient than vehicles?