# Overview

SliDeRulE (Safety in Design Risk Evaluator) for buildings is a tool to assist building designers with assessing the construction safety risk associated with their designs. SliDeRulE is intended for use during the design phase of a building. As a building is being designed, architects and engineers can use SliDeRulE to: determine the level of safety risk associated with their design; compare prospective designs based on construction safety risk; and create building designs that minimize the risk of construction worker injury.

SliDeRulE features:

• Applicable to multi-story buildings
• Assess an entire building, a specific building system, or each of the many design features within a building.
• Evaluate nine different building systems containing a total of 141 possible design elements. See the building systems and design elements.
• Considers the risk of near misses and low, medium, and high severity injuries
• Accounts for the amount of worker exposure based on building size and material quantities

## SliDeRulE risk factors

SliDeRulE uses risk factors to calculate safety risk. The risk factors are based on the frequency of an incident occurring, severity of a potential incident, and duration of worker exposure to the hazards associated with constructing each design element.

• Frequency is the expected number of incidents over time for a specific severity level (e.g., 1 injury per 10,000 worker-hours). The units of frequency are: incidents per worker-hour (incidents/w-hr).
• Severity is the magnitude of the incident/injury. The units of severity are: severity/incident. SliDeRulE incorporates four severity levels:
• Near miss:  Disrupting incident that could have resulted in an injury. No impact on work time
• Low severity:  Temporary discomfort/pain or minor first aid required. Limited impact on work time; worker can return to regular work within one day.
• Medium severity:  Major first aid required or medical case. Worker could not return to regular work within one day (lost work time).
• High severity:  Permanent disablement or fatality. Worker could not return to work at all.

SliDeRulE uses a geometric scale for the impact value of each severity level, starting with 1 for near miss and increasing geometrically to 14,282 for high severity.

• Worker Exposure is the amount of time required to construct the design element. The units of worker exposure are hours per unit of the design element. For example, for piping, the exposure is the number of worker hours required to install one linear foot of pipe (w-hr/LF).

The risk factor associated with a design element is calculated as follows:

$Risk \: factor (severity/unit) = Frequency (incidents/w-hr) \times Severity (severity/incident)\times Exposure (w-hr/unit)$

SliDeRulE includes risk factors for all of the building systems and design elements. The risk factors were developed based on statistical analyses of frequency, severity, and exposure data from a diverse sample of experienced general and trade contractor site personnel who construct each of the elements.

## How it works

For each design element contained in a building design, the user enters the quantity of the design element into SliDeRulE (e.g., 100 linear feet of pipe, 500 cubic yards of concrete, or 200 square feet of roofing). SliDeRulE then uses the entered quantities to calculate the safety risk associated with each design element, building system, and the entire building.

$Design \: element \: risk\: (severity) = Risk\: factor\: (severity/unit) \times Quantity\: (units)$

$Total\: design\: risk\: (severity) = Sum\: of\: Design\: element\: risk\: for\: all\: elements\: (severity)$

The risk is calculated for an entire building, each building system, and each of the design features included within the building. Risk values may be calculated for different design options and then compared to optimize the design based on safety risk.

## Interpreting the results

SliDeRulE calculates and reports a numerical risk value. A lower risk value indicates a safer design for construction workers who are constructing the building.The risk value for one design may then be compared to that of another design in order to select the best possible design for preventing construction worker injuries and fatalities.

SliDeRulE can calculate risk to a level of precision that is likely more than needed in practice. The design is just one of many factors on a project which influence safety. As a result, a small difference in the calculated risk values of two designs may not translate into a difference in safety on the jobsite. A large difference in risk values, however, would indicate to the designer that a safety concern is likely present and that the design should be reviewed accordingly.