3.3 Travel Types (Type 1, Type 2, Type 3) & IPAF Categories

Travel Kinematics (Type 1, Type 2, Type 3)

Quick Answer: While Groups (A and B) classify whether the platform centre can move outside the tipping lines, Travel Types (1, 2, and 3) classify how and when a MEWP can travel. Type 1 allows travel only in the stowed transport position (requiring outriggers to elevate); Type 2 permits elevated travel controlled from the chassis; and Type 3 permits elevated travel controlled directly from the work platform console.

The ability of a MEWP to travel across a worksite—either stowed or elevated—directly dictates its productivity and its operational hazard profile. BS EN 280 establishes a rigid kinematic classification system based on machine travel capabilities.

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The Kinematic Matrix: Groups vs. Travel Types

In powered access engineering, the combination of Group (A or B) and Type (1, 2, or 3) defines the machine's complete kinematic classification and maps directly to the standard categories used across the industry (such as IPAF categories):

Kinematic Classification Matrix:

                 | Type 1: Stowed Travel Only | Type 3: Platform Elevated Drive
-----------------+----------------------------+---------------------------------
Group A:         | Category 1a                | Category 3a
(Always inside)  | (Static Vertical)          | (Mobile Vertical / Scissor)
-----------------+----------------------------+---------------------------------
Group B:         | Category 1b                | Category 3b
(May be outside) | (Static Boom / Outrigger)  | (Mobile Boom / Self-Propelled)

(Note: Type 2 machines exist in both groups but are uncommon, specialised plant, such as some aircraft-maintenance platforms (2A, 2B) and certain underbridge or rail-mounted units. IPAF trains these under its Special category.)

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Type 1 Kinematics: Stowed Travel Only

Under BS EN 280, Type 1 MEWPs are defined by a strict operational parameter: travelling is ONLY permitted when the machine is in its stowed / transport position.

Operational and Engineering Characteristics

• Elevation Prerequisites: Many Type 1 machines (truck-mounts, trailer-mounts, spider lifts and outrigger-equipped verticals) must deploy outriggers, stabilisers or levelling jacks to achieve a level, stable base before the platform can rise. Push-around verticals (PAVs) are also Type 1 but elevate on their wheels with the brakes applied, on level ground.
• Outrigger Interlock System: Where stabilisers are needed for stability, the design must prevent the platform being raised until they are correctly set. Microswitches and hydraulic pressure transducers on each outrigger leg verify that all feet are bearing load and that the chassis is level (typically within $\le 1^\circ$). If any single outrigger loses ground contact or pressure, the electrical interlock instantly disables all boom and lift functions.
• Drive Lockout: As soon as the platform leaves its transport cradles or outriggers begin extension, the drive propulsion system is mechanically or electrically locked out. The machine cannot be moved until the platform is fully lowered, stowed, and outriggers are retracted.

Typical Type 1 Machines

• Category 1a (Static Vertical): Vertical mast lifts or vertical platforms equipped with outriggers, push-around vertical units that must remain stationary when elevated.
• Category 1b (Static Boom): Vehicle-mounted cherry pickers (mounted on van, truck, or flatbed chassis), trailer-mounted booms, and crawler spider lifts equipped with wide-spread outrigger legs.

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Type 2 Kinematics: Elevated Travel Controlled from Base

Under BS EN 280, Type 2 MEWPs are defined as: machines where travelling with the platform in an elevated position is controlled EXCLUSIVELY from a control position situated on the chassis or base.

Specialised Use

Type 2 machines are rare in general construction and facilities work because of the risks of controlling elevated travel from the ground:

• Blind Spots & Crushing Hazards: The ground operator controlling chassis drive cannot feel or accurately judge overhead entrapment hazards, structural pinch points, or dynamic swaying experienced by the elevated occupant.
• Specialist Applications: Type 2 designs appear in specialist plant such as some rail-mounted maintenance vehicles, underbridge units and aircraft-maintenance platforms, where a driver positions the base while others work from the platform. IPAF classes such machines as Special, and they need specific training and familiarisation.
• Essential Precautions: Type 2 operation relies on reliable two-way communication between the driver and the platform occupants, warning devices, and the low elevated travel speeds set by the manufacturer.

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Type 3 Kinematics: Elevated Travel Controlled from Platform

Under BS EN 280, Type 3 MEWPs are defined as: machines where travelling with the platform in an elevated position is controlled DIRECTLY from a control console situated within the work platform itself.

Type 3 Elevated Travel Kinematics:

      [ Platform Control Console ]  <--- Operator drives, steers, & elevates
      [   (Occupant in Platform) ]       directly from aloft
                  |
                  v
            (Elevated Boom / Scissor)
                  |
                  v
             [ Chassis ]
           [Drive Wheel]     <--- Wheels powered while platform is aloft

Operational Characteristics

Type 3 represents the vast majority of mobile powered access equipment across global construction and industrial maintenance:

• Category 3a (Mobile Vertical): Self-propelled electric or rough-terrain scissor lifts.
• Category 3b (Mobile Boom): Self-propelled articulating boom lifts and telescopic boom lifts (cherry pickers).

Safety Hazards of Type 3 Operation

Operating a machine while elevated gives the operator autonomy to reposition without descending. However, it introduces grave hazards:

• Dynamic Bounce (The Catapult Effect): Driving over an obstacle as small as a 50 mm piece of timber or a kerb edge causes the chassis to tilt momentarily. At a 20-metre platform height, this small base deflection acts as a catapult, violently whipping the basket and ejecting unrestrained occupants.
• Overhead Crushing: The operator, facing forward while driving, may fail to notice an overhead structural beam, pipe rack, or lintel behind or above them, leading to fatal chest or neck entrapment against the control console.
• Blind Driving: When elevated, the operator's view of the floor immediately around the tyres is obscured by the chassis and scissor stack/counterweight.

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Critical Safety Interlocks & Electronic Safeguards

To mitigate the hazards inherent in Type 3 elevated travel, BS EN 280 mandates several multi-redundant electronic and mechanical interlocks.

1. Transport Height Limit Switches & Speed Attenuation

MEWPs feature two distinct drive speed modes:

• High Travel Speed (Stowed Position): When the machine is fully lowered into its transport cradle, high drive speed is enabled (typically $3.5$ to $5.0\text{ km/h}$) to facilitate transit between work areas.
• Elevated Creep Speed: As soon as the platform is raised beyond the manufacturer's stowed or transport position (sensed by limit switches), high speed is electrically locked out. The drive controller automatically throttles down to micro/creep speed (typically $\le 0.8\text{ km/h}$ or $0.5\text{ mph}$).

2. Pothole Protection (PHP) Systems

On Category 3a slab scissor lifts, ground clearance in the stowed position is approximately 100 mm to allow transit over minor surface irregularities. However, driving while elevated with a 100 mm ground clearance creates a severe overturn hazard if a wheel encounters a void or trench.

• Mechanics: As the scissor stack elevates above transport height, mechanical linkages or hydraulic actuators deploy steel pothole protection bars (skirts) along both sides of the chassis base.
• Safety Clearance: These skirts drop down to reduce ground clearance to just 15 mm to 20 mm.
• Overturn Arrest: If a wheel drives into a floor hole, open trench, or depression, the deployed pothole bar contacts the ground surface almost immediately, catching the chassis weight and preventing the machine from tilting to its overturning angle.
• Drive Interlock: If the pothole protection bars fail to deploy fully (e.g., due to debris jamming the mechanism), limit switches detect the fault, sound a continuous alarm, and completely disable all drive and lift-up functions.

Pothole Protection (PHP) Interlock Sequence:
[Platform Rises > Transport Height] ---> [Limit Switch Triggers PHP Skirts]
                                             |
                                             v
                              [Skirts Drop to 15-20 mm Clearance]
                                             |
                         +-------------------+-------------------+
                         |                                       |
                   [PHP Deployed]                         [PHP Jammed/Failed]
                         |                                       |
                         v                                       v
             [Creep Travel Permitted]               [Drive & Lift Cut-Out / Alarm]

3. Dual-Axis Tilt Sensor Interlocks

Type 3 MEWPs incorporate solid-state electronic inclinometers. If the chassis exceeds the manufacturer's maximum allowable tilt angle (typically 1.5° to 3° for slab machines and 3° to 5° for rough-terrain booms):

• An audible alarm sounds continuously on both platform and ground consoles.
• High-risk functions are immediately disabled (lift-up, boom extend, high speed drive).
• On many modern booms, drive is completely locked out when tilted while elevated, forcing the operator to retract and lower the boom within safe envelope limits.

4. Dead-Man Controls

All Type 3 travel functions require positive two-stage activation:

• A foot-switch on the basket floor or a mechanical trigger switch on the drive joystick must be held closed before any motion command executes.
• On many machines, if the foot-switch is held for longer than a set delay (a few seconds, set by the manufacturer) without a function being selected, it resets, so it cannot simply be wedged down.

Summary Matrix: Travel Kinematics Types