●The weather  is extremely variable  (Agyakwa-Baah and Chileshe, 2010;  Pavaskar et al。,   2012)

●Access to the project site is limited and resources are difficult to mobilize (Cardona et al。,  2012)

●The ground is contaminated or unsafe in spots (Agyakwa-Baah and Chileshe, 2010)

Contractual drivers ●  The organization is experiencing severe financial distress (Agyakwa-Baah and Chileshe, 2010; Berkeley et al。, 1991; Cardona et al。, 2012)

●The prices are fluctuating (Agyakwa-Baah and Chileshe,    2010)

●Payments are being delayed (Agyakwa-Baah and Chileshe, 2010)

●The client’s behavior is unpredictable (Baccarini and Archer, 2001; Johnson et al。, 2013)

●Design changes and delayed approvals continue to occur during the construction phase (Agyakwa-Baah and Chileshe, 2010)

●Schedule and cost estimates are produced before designs are completed (Pavaskar et al。, 2012)

●Contract strategy seems to be based on unrealistic assumptions (Berkeley et al。, 1991; Johnson et al。, 2013)

Managerial drivers ●  The project is suffering a delayed start (Berkeley et al。, 1991)

●Tasks are taking longer than planned (Berkeley et al。,    1991)

●Quality control is not in place (Agyakwa-Baah and Chileshe, 2010)

●Appropriate insurance is not in place (Johnson et al。, 2013)

●The procuring team lacks maturity and knowledge (Agyakwa-Baah and Chileshe, 2010; De Marco and Thaheem, 2013; Graham et al。, 2010a)

●Workers have inertia to implement contingency plans (Graham et al。, 2010b)

●Foremen are favoring incentives that may become perverse (Graham et al。, 2010b)

Communicational drivers

●

Large amount of data is required to describe each task (Ramasesh and Browning, 2014)

●Project tasks are considerably dependent on a particular industry (Berkeley et al。, 1991)

●Frequent use of jargons is indispensable (Ramasesh and Browning, 2014)

●Information is of a low quality and element definitions are rather equivocal (McLain, 2009; Ramasesh and Browning, 2014)

●Communication is affected by information asymmetries (Graham et al。, 2010b; Johnson et al。, 2013)

●Project team members are facing language problems (Berkeley et al。, 1991)

●Stakeholders express conflicting or widely pergent viewpoints (Graham et al。, 2010a; Ramasesh and Browning, 2014; Seifert, 2008)

Internal drivers ● The project will end up with a technologically unique structure (Baccarini and Archer, 2001; Johnson et al。, 2013)

●The systems used in the procurement process have numerous possible states, positive feedback or large scale up (Graham et al。, 2010b; Ramasesh and Browning, 2014)

●Project elements are of great complexity, novelty, fragility, sensitivity or variety, or they lack resilience, coping, adaptation, buffering, or change absorption capacities (Baccarini and Archer, 2001; Berkeley et al。, 1991; Cardona et al。, 2012; Cooper et al。, 2005; Graham et al。, 2010b;  Johnson et  al。,  2013; Ramasesh  and  Browning, 2014)

●Numerous, critical, perse or external relationships appear between project elements (Ramasesh and Browning, 2014)

●Speed is of extraordinary importance (Baccarini and Archer, 2001)

●Extra intensive effort is often required to perform the project tasks (Baccarini and Archer, 2001)

●Safety margins are relatively narrow (Graham et al。, 2010b; Ramasesh and Browning, 2014)

450 H。 Malekitabar et al。 / Safety Science 82 (2016) 445–455

9。The definition of the drivers is dependent to a large degree on the way the objects and their boundaries are defined (Ramasesh and Browning,  2014)。