## 1 Introduction  
The distribution environment includes the handling, storage, and transport operations that a product is subjected to as it is moved from the manufacturing facility to the final customer [1]. Within the distribution environment, several hazards have the potential to damage products, such as compression, vibration, and shock events. Mechanical shock occurs when a packaged item's position, velocity or acceleration suddenly changes. Shock can be characterised by a rapid increase in acceleration followed by a fast decrease over a relatively short time duration. A longitudinal shock of a package in a unit load may typically be 10 ms (0.010 s) long and have a magnitude around or over 4G. [2] Shock events include sudden stops in transportation, drops during manual handling, and impacts during distribution; basically, any event which causes a drastic change in a short period of time [3]. Because of the high probability that products will face distribution hazards before reaching the final customer, packaging engineers must ensure their products and containers can withstand these hazards. A thorough understanding of the risks to which the package is exposed to during distribution, and an efficient distribution loss tracking system are useful to aid in the design of cost-efficient packaging solutions that will protect products and prevent damage. Equipment such as forklifts and pallet jacks are ubiquitous in modern warehouses [4]. Due to excessive handling, there is a high potential of this equipment causing damage to pallets. Fork tines are listed as the fourth most common cause of damage, after protruding snails, dropped boxes, and hitting the bars in racks [1]. Pallet testing standards are often used to simulate the damage caused by forklift handling in laboratory settings. ASTM 1185 [5] and ISO 8611 [6] both incorporate incline impact tests that stress the pallet deck edges, blocks, and stringers in order to determine their resistance to impacts by forklifts. The effect of forklift handling is also incorporated into the ISTA 3B testing standard, which includes a pallet handling sequence that simulates damage caused by the forklift [7]. In 1993, Virginia Tech developed a comprehensive pallet durability simulation, called FasTrack, where the overall life of a pallet is assessed using a handling sequence that mimics what pallets experience in the field from industrial forklifts and pallet jacks [8]. Knowledge of the locations and types of damage experienced by pallets during forklift handling can help to improve the durability of pallet designs. It was observed that pallets used in the field feature a high percentage of top lead deckboard and stringer damage, which is often caused by the use of forklifts and pallet jacks. [PERSON] and [PERSON] used this information to investigate the effect that selectively placing high-quality wood on the edges and ends of the pallet would have on pallet durability [9]. This information has been used in standards and industry guidelines, such as the ASME MH1-1997 [10]. An extensive number of research projects have focused on understanding the vibration environment of common transportation modes such as parcel trucks [11; 12], rail cars [13; 14], and industrial trucks [15], as well as vibration transmissibility in a unit load [16]. The influence of different factors, such as speed, top load and suspension, have been extensively investigated too [17; 18; 19]. With this information, recommendations regarding how to simulate these conditions have been proposed [20]. Meanwhile, only a limited number of research projects have focused on the investigation of shock impacts during material handling [21]. More information is needed on the effects that factors such as the weight of the load and the speed of the forklift have on shock damage. [PERSON] et al. equipped pallets and unit loads with sensors to measure the level and transmissibility of shock impacts during forklift handling for three different unit load configurations.