IRSST - Institut de recherche Robert-Sauvé en santé et en sécurité du travail

Use of Two-post Aboveground Automotive Lifts
Identification of technical determinants for stability and work determinants for automotive technicians


This research deals specifically with the use of two-post aboveground (2PAG) automotive lifts. These lifts are used by automotive technicians during vehicle maintenance and repair, and require them to work under or near an elevated load weighing several tons. The death of a young technician in 2014 prompted the automotive repair industry to request this research. This study targeted the risk of a vehicle falling from one of these 2PAG lifts.

Many factors can contribute to a vehicle falling from a 2PAG lift. During preparation for the project, technical, organizational and human factors were discussed. However, there was limited knowledge about how these factors contribute to the manner in which a vehicle is lifted or to work determinants. The objective of this project was therefore to identify and categorize the main technical determinants of lifting stability using a 2PAG lift and the main work determinants underlying the adoption of lifting methods used in garages.

A multi-disciplinary engineering and ergonomics approach was chosen to respond to an issue related to both the mechanical functioning of the equipment and its use. The methodology chosen enabled an exploration of several data sources: lifting tests with measurements, interviews with various actors in the industry, field observations, documentation and testing of inspection checklists. More specifically, the project was structured around three blocks:

  • Block A (two complete experimental designs): Measuring and comparing the induced distribution of forces in the lift arms and the slipping of the vehicle on the support pads using various configurations to identify the most significant factors.
  • Block B (seven preliminary interviews with key actors in the sector, recruitment of five garages with 108 lifting situations observed, 19 preliminary interviews and eight in-depth interviews): documenting the operating procedures related to use of 2PAG lifts and identifying the determinants of the lifting activity carried out by technicians.
  • Block C (aggregation of data sources from the different blocks): formulating qualitative and quantitative verification criteria to improve the periodic inspection of 2PAG lifts.

Although the project was conducted in blocks, a co-construction approach was used and results were pooled throughout the project so that each block would contribute to the others.

In particular, the analysis of the experimental designs in Block A showed that:

  • during some tests with the compact vehicle on the more well-worn lift, measurements revealed that one arm was being underused (<50 kg), increasing the risk of it pivoting. This phenomenon observed with the most well-worn lift highlights the importance of lift condition.
  • for the pick-up truck, the loading of the box and the setback from the posts led to a significant load imbalance on the rear arms (up to 82% of the total moments generated). These configurations should be avoided.
  • the fall arrest latches that are positioned asymmetrically in the posts put more load on the two arms on the side of the latches. This configuration is not recommended.
  • the initial positioning of the support pads is essential, given that slippage of up to one quarter of the pad width (>50 mm) was measured during testing. Locking the arms did not have a significant effect on the slippage measured.
  • the slippage measured was significantly greater with the foldable steel pads than with the rubber pads. The same is true with lateral impacts compared to pushing down on the trunk.

The data collection from Block B provided the following insights. Vehicle lifts are being used in Québec in a context of major transformations in both the automotive market and the trade of automotive technician. Beyond these transformations, technicians are faced with a wide range of lifting situations, some of which cause difficulties that can be explained by (1) the characteristics and condition of the vehicles and their lifting points (e.g., vehicle weight and width, location and degradation of lifting points, lack of clearly identified alternative lifting points); (2) the characteristics of the lifts used and their installation (e.g., areas within reach of the pads, limited possibility of adjusting pads, interference of the arms with the vehicle, slope of the floor); (3) the work to be performed on the vehicle (e.g., arm and pad position getting in the way of the technician, change in centre of gravity, possibility of doing the work on another type of lift); (4) the context (e.g., winter/ice, busy period during seasonal tire changes, performance-based work organization). The results also show frequent mismatches between the lift and the vehicle to be raised. In addition, they reveal that learning how to lift safely takes time and that organizational support plays an important role. Experienced technicians understand the vehicles and their characteristics, are able to assess the situation, to decide how or whether to hoist them on their lift, to make compromises (position of the vehicle or the support pads) and sometimes to “jerry-rig” something (such as using hockey pucks) to compensate for the lack of versatility of their lift. The procedures advocated by accident prevention organizations for lifting have distinct and universal steps. However, the actual process is to go back and forth between assessing and re-assessing (repositioning the vehicle or the support pads) when access to the recommended lifting points is problematic or stability appears to be compromised. Finally supervisory staff can play a supportive role by rejecting vehicles that are too heavy or too rusty and by involving experienced technicians in the process of purchasing these lifts.

The work in Block C, with respect to 2PAG lift inspection, led to the development of an inspection checklist specific to these lifts, including 15 inspection points broken down into 42 sub-inspection points and 74 inspection criteria. For each inspection criterion, an inspection frequency was established using a criticality decision algorithm.

Pooling all the results made it possible to identify several avenues for accident prevention. The first concerns the vehicle and 2PAG lift manufacturers in terms of the design of their respective products. The second targets legislation and, more specifically, training and inspection requirements. The third applies to automotive garages as the entities that purchase, install and maintain lifts, raise customer awareness, and organize and assign work in the most complex cases. The fourth pertains more directly to garage staff, including technicians and supervisors, with regard to training content on the range of situations and the conditions required to ensure lifting stability.

Additional Information

Category: Research Report
Research Project: 2018-0002
Online since: April 27, 2023
Format: Text