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Brake vacuum booster characteristics are of great importance to understanding overall brake system operation in light vehicles so equipped. In recent years, engineering reports relevant to traffic crash reconstruction have discussed, among related areas, the operation of brake booster systems at high applied brake pedal force levels and with various levels of vacuum available within the booster. A vehicle-testing framework is presented for characterizing and understanding the operation of a vacuum booster with pedal force ranging above the vacuum runout point, as well as booster operation relative to varying levels of available vacuum and patterns of depletion of stored vacuum. Concepts are illustrated with measurements of exemplar vehicles. The objective of this paper is to promote improved understanding of brake booster operation and to advance more precise articulation of related concepts within the crash reconstruction community.

With commercial availability of the Bosch Crash Data Retrieval Tool (CDR), the information stored in vehicle Event Data Recorders (EDRs) has increasingly been used to supplement traditional traffic crash data collection and reconstruction methods, allowing enhanced confidence levels in transportation safety research. The objective of this study was to assess the accuracy and reliability of EDR data images obtained with the Bosch CDR tool by comparing them to a known crash impulse. Multiple EDRs and necessary sensor arrays were mounted on a HYGE™ acceleration-type crash simulation sled system at various orientations representing different principal direction of force (PDOF) angles and subjected to controlled “crash” impulses, simulating a “deployment event” (DE) and triggering data to be saved in the EDRs. The data included in each EDR's CDR report was compared to the known conditions of the impulse.

Prior to the widespread implementation of ABS brake technology in light vehicles, driver training often included instruction to “pump the brakes” to avoid locking the wheels. Many driver education programs now recommend maintaining high brake pedal force and relying on ABS. It is sometimes asserted that drivers desiring to stop a vehicle quickly still “pump the brakes”. Investigators sought to understand whether drivers desiring to decelerate quickly pump the brakes, especially in a way that may deplete the vacuum stored in a vehicle's brake booster if so equipped, or whether they apply the brakes in a manner corresponding to their desired deceleration. The National Highway Traffic Safety Administration (NHTSA) conducted a testing program to examine driver braking behavior in crash avoidance maneuvers.