Prediction of wearing comfort of bicycle helmets

• Research unit: COST
• Project number: C11.0137

Key words (English)

Manikin head form; bicycle helmet; thermoregulation; thermal comfort; prediction model

Research programs (English)

COST-Action TU1101 - Towards safer bicycling through optimization of bicycle helmets and usage

Short description (English)

The wearing rate of bicycle helmets can be attributed, at least in part, to the thermal discomfort that occurs while wearing a helmet. Ventilation and radiant shielding characteristics are the main factors which affect thermal strain and wearing comfort of a bicycle helmet. To simulate thermoregulatory responses of wearing a bicycle helmet and estimate its effect on thermal comfort, we use a manikin head form. Manikin experiments provide more objective data at lower variability compared to human subject trials. Such data are prerequisite for a systematic understanding of thermal effects of headgear. We aim at developing a new multi-section manikin head form coupled with a mathematical model of physiological responses which is prerequisite to investigate local differences in heat transfer of the head. This will allow a systematic analysis of the effect of individual bicycle helmet vents on cooling power and radiant heat transfer. Our goal is to identify local regions of the head where thermal discomfort is perceived. This contributes to the understanding of the effect of environmental conditions and helmet vent design on the perception of (local) thermal discomfort. Furthermore, optimized helmet ventilation improves head cooling. We aim at understanding the effect of improved head cooling on whole body thermoregulation and exercise performance. The investigations provide new knowledge for the development of bicycle helmets with improved thermal characteristics.

Further information (English)

Full name of research-institution/enterprise: Eidg. Materialprüfungs- und Forschungsanstalt EMPA Abteilung Schutz und Physiologie

Partners and International Organizations (English)

BE; HR; DK; FI; FR; DE; EL; IE; IL; IT; NL; NO; PT; RO; SI; ES; SE; UK; AU

Abstract (English)

The wearing rate of bicycle helmets can be attributed, at least in part, to the discomfort that occurs while wearing a helmet. Ventilation and radiant shielding characteristics are main factors which affect thermal strain and wearing comfort of a bicycle helmet. To systematically investigate heat and mass transfer of bicycle helmets and concomittant thermoregulatory responses as well as its effect on thermal comfort, a thermal head manikin is used. Manikin experiments provide more objective data at lower variability compared to human subjects trials. Such data are prerequisite for a systematic understanding of thermal effects of headgear and how it can be optimised by design adjustments. This new methodology provides important inputs for the industry to develop new helmet designs with improved thermal comfort and, thus, increasing the acceptance of users. A new nine-zone thermal head manikin coupled with a mathematical model of thermo-physiological responses was developed and validated in this project. It was concluded that the nine-zone thermal head manikin provided high spatial resolution when investigating heat transfer at head-site. Local heat transfer through headgear could be accurately quantified in several realistic situations accounting for different environmental conditions and air speeds in occupational, traffic or sport headgear applications. However, the inter-test variability for more precise calculated variables, such as the radiant heat gain can be further improved to achieve more precise thermal assessment of helmets. The characteristics of the head manikin allow for representing the human head physiology in terms of segmentation, heat transfer and responsiveness. Some inaccuracies in heat flux measurements were observed for high temperature gradients occurring on the head surface, particularly at forehead and face. Thus, a wide characterization of heat flux deviation and eventual correction of the zone’s lateral insulation would further increase the precision of the coupled system. The build-up of a human experiment data base and the validation of the physiological model by Fiala proofed the importance of accurately reporting the experimental scenario such as clothing fitting, local environmental conditions for body parts and the temperature measuring method for ensuring the reliability of the model predictions. The physiological model by Fiala was successfully coupled with a head manikin to build up the thermophysiological head simulator. The comparison of the prediction of the coupled system with human experimental data in several scenarios combining different environmental temperatures and activity levels showed a good agreement in predictions of rectal and mean skin temperatures. It was found that the skin fabric applied on the head manikin plays a crucial role for accurate simulations in warm-exercising conditions.

References in databases (English)

Swiss Database: COST-DB of the State Secretariat for Education and Research Hallwylstrasse 4 CH-3003 Berne, Switzerland Tel. [phone] Swiss Project-Number: C11.0137