Handling capacity
13.0 %
Section layout
Role → Design method → Worked numbers → Software → Code. The design driver here is unusual: it starts with a traffic simulation, which then dictates the number, speed, size and arrangement of every lift. Symbols & constants used in the worked examples
| Symbol | Meaning |
|---|---|
| P | Passengers carried per trip (≈ 80% of car capacity). |
| L | Number of lifts in the group. |
| U | Population served by that group. |
| RTT | Round-trip time (seconds) — from the traffic simulation. |
| 300 | The number of seconds in 5 minutes (handling capacity is measured per 5 min). |
Key formulas: handling capacity HC% = (300·P·L) ÷ (RTT·U) × 100 · waiting interval Interval = RTT ÷ L · travel time t = distance ÷ speed
6.1 Traffic analysis — the starting point
Role: determine how many lifts, of what speed and size, satisfy the building population's demand at peak (up-peak in the morning, or two-way/lunch peaks). Two key metrics:
- Handling capacity (HC%) — the % of the population a group can move in 5 minutes. Targets: offices ~11–15%, residential/hotel lower.
- Interval (waiting) — average time between car arrivals at the main lobby; target ≤ ~25–30 s (offices).
Both come from the Round-Trip Time (RTT) — the time for one car to serve a full up-peak cycle:
HC% = (300 · P · L) ÷ (RTT · U) × 100 | Interval = RTT ÷ L
P = passengers carried per trip (≈80% of car capacity), L = number of lifts in the group, U = population served by the group, RTT in seconds.
Lift group: handling capacity & interval vs car count
5-minute handling capacity HC% = 300·P·L ÷ (RTT·U), and waiting interval = RTT ÷ L. More cars raise capacity and cut waiting — at the cost of shaft space, which is why tall towers zone and use sky-lobby shuttles. (P = 13 passengers/car.)
Cars serving the zone from the main lobby.
People in the zone this group serves.
Time for one car to complete an up-peak cycle (from the simulation).
Interval
30 s
Cars selected
6
Office target
Bars: 5-min handling capacity for each group size; line: interval. Your selected group is highlighted. Office target ≈ 11–15% HC and ≤ 25–30 s interval.
Worked example 6.1 · Size a lift group for a zone
Given: rise zone population U = 1,000; car capacity 1,600 kg ≈ 21 persons, filled to ~62% → P = 13/trip; calculated RTT = 180 s; group of L = 6 lifts.
HC% = (300 × 13 × 6) ÷ (180 × 1,000) × 100 = 23,400 ÷ 180,000 × 100 = 13.0% (meets office target).
Interval = RTT ÷ L = 180 ÷ 6 = 30 s .
6 lifts per zone meet both targets. If population were higher or RTT longer, you add lifts or split into more rise zones / add shuttles — the core of tall-building lift planning.
In the software
Run up-peak and full-day simulations in Elevate (Peters Research) (or manufacturer traffic tools): enter floor populations, heights, car size/speed, door times, and dispatch algorithm → it computes RTT, HC%, interval and queue lengths for each configuration. Iterate car count/speed/zoning until targets are met. Code & guidance
Traffic design: CIBSE Guide D (Transportation in Buildings); ISO 8100 / ISO 4190; manufacturer data.6.2 Arrangement & zoning (sky lobbies, double-deck, shuttles)
Role: you cannot run one set of lifts the full height — it wastes core space and time. The building is split into rise zones, each served by a local group, plus high-speed shuttle lifts to sky lobbies where occupants transfer. Double-deck cars (two cabins serving two floors at once) and shuttle expresses are used in super-tall towers to maximise capacity per shaft.
Why zoning saves the core
Lift shafts consume valuable floor plate. Zoning + sky-lobby shuttles + double-deck cars move more people through fewer shafts, freeing rentable/usable area — a major architectural-MEP trade-off. Code
Arrangement & capacity: CIBSE Guide D; ISO 8100; fire/egress interface: SBC 801 / NFPA 101.6.3 Lift types & drive
| Type | Use |
|---|---|
| Gearless traction (PM/AC, VVVF drive) | Standard for mid/high-rise & high speed — efficient, smooth |
| Machine-Room-Less (MRL) | Low/mid-rise where no machine room is wanted |
| Double-deck / shuttle | Super-tall — capacity & express runs to sky lobbies |
| Hydraulic | Very low rise only (not for towers) |
The rope problem at height
Conventional steel hoist ropes become too heavy to lift their own weight beyond ~500 m rise, forcing a transfer/shuttle. Carbon-fibre belts (much lighter & stronger) extend single rises toward ~1,000 m — a key enabler of megatall single-shaft runs. Code
Lift safety: EN 81-20/-50 (Europe) or ASME A17.1/CSA B44 (US); choose the basis per project spec; ISO 8100.6.4 Machine, ropes, counterweight, rails & safeties
Role: the traction machine (motor + sheave) drives the roped car against a counterweight (≈ car + 50% load, to balance and cut motor size); guide rails align car & counterweight; safety gear, overspeed governor and buffers stop the car safely.
Worked example 6.4 · Travel time & speed
Given: a shuttle serving a sky lobby 400 m up; rated speed 8 m/s.
Pure run time = 400 ÷ 8 = 50 s, + acceleration/deceleration + door times (~10–15 s) ≈ ~65 s per trip.
Speed is chosen so express trips stay acceptable: super-tall shuttles run 8–10+ m/s. Higher speed shortens RTT (feeds 6.1) but raises cost and needs pressure-controlled cabs for ear comfort.
Code
Components & safeties: EN 81-20/-50 / ASME A17.1; ropes/suspension & factors of safety per the adopted code.6.5 Shaft, pit, headroom & lobby (the builder's-work)
Role: the lift needs a code-compliant shaft (size, smoke venting/pressurisation), a pit (buffer/clearance below the lowest floor) and headroom (clearance above the top floor), plus lobbies sized for waiting crowds. These dimensions come from the manufacturer's drawings + code clearances and are a key structural-MEP coordination item.
Code
Shaft/pit/headroom clearances: EN 81-20 / ASME A17.1; shaft pressurisation & fire: NFPA 92/101, SBC 801.6.6 Firefighting lifts & fire operation
Role: dedicated firefighting lifts let the brigade reach fire floors and serve as part of the evacuation strategy; all lifts perform fire recall (return to a designated floor and park) on alarm. Critical and mandatory in tall buildings.
| Function | Standard |
|---|---|
| Firefighting lift (protected lobby, power, water protection) | EN 81-72 |
| Lift behaviour in a fire (recall logic) | EN 81-73 |
| Landing-door fire resistance | EN 81-58 |
| Occupant evacuation lifts (where used) | EN 81-76 / code & AHJ |
Code
EN 81-72/-73/-58/-76; fire recall & standby power: SBC 801 / NFPA 101 / 110; AHJ = Civil Defense.6.7 Escalators & moving walks
Role: high-capacity transport between a few levels (podium, retail, lobby). Sized by step width and speed for throughput; safety features (combs, brakes, balustrades) per code.
Worked example 6.7 · Escalator capacity
Given: 1,000 mm step width (≈ theoretical 9,000 persons/h nominal; realistic ~6,000–7,500 persons/h at 0.5 m/s).
Use the realistic throughput (not the theoretical maximum) for design; provide enough units for the podium/retail peak flow.
Code
Escalators/moving walks: EN 115 / ASME A17.1; capacity guidance: CIBSE Guide D.6.8 Dispatch & group control
Role: the brain that assigns cars to calls. Modern towers use destination control (DCS) — passengers enter their floor at a lobby terminal and are grouped into cars by destination, cutting stops and RTT dramatically versus conventional up/down buttons. This directly improves the 6.1 metrics.
In the software
Elevate models conventional vs destination control so you can quantify the RTT/interval improvement and reduce the number of shafts needed. Code
Control & functional safety per EN 81-20 / ASME A17.1; DCS accessibility provisions.6.9 Power, regeneration & standby
Role: lifts are big, intermittent electrical loads with high starting demand. Regenerative drives feed braking energy back to the supply (a real energy saving on tall, busy lifts). Firefighting and life-safety lifts must be on standby power (Module 4) and ride through transfer.
Code
Supply & standby: SBC 401 / NFPA 110; regenerative drives & efficiency: ISO 25745 (energy), SBC 601.6.10 Installation, accessories & field tricks
| Item | Field rule / trick |
|---|---|
| Builder's-work coordination | Shaft plumbness, insert/bracket fixings, pit waterproofing & sump — agree early; errors are very costly at height. |
| Guide-rail alignment & bracket spacing | Precise alignment for ride quality & high speed. |
| Shaft pressurisation & smoke vents | Coordinate with HVAC smoke-control (Module 1) & fire (Module 3/5). |
| Machine-room cooling, sound & vibration isolation | Machine spaces need cooling (heat load to HVAC) & isolation to avoid structure-borne noise. |
| Standby power & firefighting-lift cabling | Fire-survival supply & controls to firefighting lifts. |
| JumpLifts during construction | Temporary use of the permanent shaft speeds construction of super-tall towers — plan for it. |
Code
Installation & safety: EN 81-20/-50 / ASME A17.1; seismic provisions EN 81-77; SBC 301/801.6.11 Testing & commissioning
- Load/overspeed/safety-gear & buffer tests; ride-quality & levelling; door & safety-circuit functional tests.
- Fire recall & firefighting-lift operation verified, integrated with fire alarm & smoke control — witnessed by Civil Defense.
- Traffic performance verified against the simulation; statutory inspection & certification before use.
Code
Acceptance & inspection: EN 81-20 / ASME A17.1/A17.2; fire integration: NFPA 4 / SBC 801.Terms & abbreviations
Plain-English meaning of the vertical-transport terms used in this module.
| Term | What it means (plain English) |
|---|---|
| Vertical transport (VT) | Lifts (elevators), escalators and moving walks. |
| Traffic analysis | A simulation of how people use the lifts at peak, to decide how many lifts and how fast. |
| Handling capacity (HC%) | The % of the building population the lift group can move in 5 minutes. |
| Interval (waiting time) | Average time between cars arriving at the main lobby; lower = less waiting. |
| RTT (round-trip time) | Time for one car to complete a full up-peak cycle; drives HC% and interval. |
| Up-peak | The morning rush when everyone travels up — usually the hardest case. |
| Rise zone | A band of floors served by one lift group (the building is split into several). |
| Sky lobby / shuttle | A transfer floor where people switch from a high-speed express (shuttle) lift to local lifts. |
| Double-deck lift | A lift with two stacked cabins serving two floors at once — more capacity per shaft. |
| Traction / gearless | A roped lift driven by a motor + sheave; gearless (direct-drive) is used for high speed. |
| MRL | Machine-Room-Less — the drive sits in the shaft, no separate machine room. |
| Counterweight | A weight that balances the car (≈ car + 50% load) so the motor does less work. |
| Governor / safety gear / buffer | Safety devices that detect overspeed, grip the rails to stop the car, and cushion it at the bottom. |
| Guide rails | Steel rails that keep the car and counterweight aligned in the shaft. |
| Carbon-fibre belt | A lightweight, strong replacement for steel ropes that allows much taller single rises. |
| Pit / headroom | The clearance space below the lowest floor (pit) and above the top floor (headroom). |
| Firefighting lift | A protected lift (own lobby, power, water protection) for the fire brigade (EN 81-72). |
| Fire recall | All lifts automatically return to a safe floor and park on a fire alarm (EN 81-73). |
| DCS / destination control | Passengers enter their floor at the lobby; the system groups them into cars — cutting stops and waiting. |
| Regenerative drive | A drive that feeds braking energy back to the supply, saving energy. |
| JumpLift | Temporary use of the permanent lift shaft during construction to speed the build. |
References & software map
| Task | Software | Code/standard |
|---|---|---|
| Traffic analysis (RTT, HC%, interval), DCS comparison | Elevate (Peters Research); manufacturer traffic tools | CIBSE Guide D; ISO 8100 |
| Arrangement & shaft layout | Revit + manufacturer GA drawings | EN 81-20 / ASME A17.1 |
| Energy class | Manufacturer tools | ISO 25745; SBC 601 |
- EN 81-20 & EN 81-50 (lift design & testing); EN 81-72 (firefighting lifts), -73 (fire behaviour), -58 (landing-door fire), -76 (evacuation), -77 (seismic).
- ASME A17.1 / CSA B44 (US safety code); EN 115 (escalators); ISO 8100 / ISO 4190 / ISO 25745.
- CIBSE Guide D — Transportation Systems in Buildings (traffic design).
- SBC 801 / 401 / 301; NFPA 101 / 110 / 4; Saudi Civil Defense (firefighting lifts & recall).
Note
Worked numbers teach the method; lift count, speed and zoning come from a full traffic simulation and the manufacturer's engineering. Confirm code basis (EN vs ASME) and AHJ requirements with the project spec.