Modelling discomfort: How do drivers feel when cyclists cross their path?

Many cyclist fatalities occur on roads when crossing a vehicle path. Active safety systems address these interactions. However, the driver behaviour models that these systems use may not be optimal in terms of driver acceptance. Incorporating explicit estimates of driver discomfort might improve acceptance. This study quantified the degree of discomfort experienced by drivers when cyclists crossed their travel path. Participants were instructed to drive through an intersection in a fixed-base simulator or on a test track, following the same experimental protocol. During the experiments, three variables were controlled: 1) the car speed (30, 50 km/h), 2) the bicycle speed (10, 20 km/h), and 3) the bicycle-car encroachment sequence (bicycle clears the intersection first, potential 50 %-overlap crash, and car clears the intersection first). For each trial, a covariate, the car's time-to-arrival at the intersection when the bicycle appears (TTAvis), was calculated. After each trial, the participants were asked to report their experienced discomfort on a 7-point Likert scale ranging from no discomfort (1) to maximum discomfort (7). The effect of the three controlled variables and the effect of TTAvis on drivers' discomfort were estimated using cumulative link mixed models (CLMM). Across both experimental environments, the controlled variables were shown to significantly influence discomfort. TTAvis was shown to have a significant effect on discomfort as well; the closer to zero TTAvis was (i.e., the more critical the situation), the more likely the driver reported great discomfort. The prediction accuracies of the CLMM with all three controlled variables and the CLMM with TTAvis were similar, with an average accuracy between 40 and 50 % for the exact discomfort level and between 80 and 85 % allowing deviations by one step. Our model quantifies driver discomfort. Such model may be included in the decision-making algorithms of active safety systems to improve driver acceptance. In fact, by tuning system activation times depending on the expected level of discomfort that a driver would experience in such situation, a system is not likely to annoy a driver.

How do drivers negotiate intersections with pedestrians? The importance of pedestrian time-to-arrival and visibility.

Forward collision warning (FCW) and autonomous emergency braking (AEB) systems are increasingly available and prevent or mitigate collisions by alerting the driver or autonomously braking the vehicle. Threat-assessment and decision-making algorithms for FCW and AEB aim to find the best compromise for safety by intervening at the "right" time: neither too early, potentially upsetting the driver, nor too late, possibly missing opportunities to avoid the collision. Today, the extent to which activation times for FCW and AEB should depend on factors such as pedestrian speed and lane width is unknown. To guide the design of FCW and AEB intervention time, we employed a fractional factorial design, and determined how seven factors (crossing side, car speed, pedestrian speed, crossing angle, pedestrian size, zebra-crossing presence, and lane width) affect the driver's response process and comfort zone when negotiating an intersection with a pedestrian. Ninety-four volunteers drove through an intersection in a fixed-base driving simulator, which was based on open-source software (OpenDS). Several parameters, including pedestrian time-to-arrival and driver response time, were calculated to describe the driver response process and define driver comfort boundaries. Linear mixed-effect models showed that driver responses depended mainly on pedestrian time-to-arrival and visibility, whereas factors such as pedestrian size, zebra-crossing presence, and lane width did not significantly influence the driver response process. Drivers released the accelerator pedal in 99.8 % of the trials and braked in 89 % of the trials. Forty-six percent of the drivers changed their negotiation strategy (proportion of pedal braking to engine braking) to minimize driving effort over the course of the experiment. In fact, 51 % of the of the inexperienced drivers changed their response strategy whereas only 40 % of the experienced drivers did; nevertheless, all drivers behaved similarly, independent of driving experience. The flexible and customizable driving environment provided by OpenDS may be a viable platform for behavioural experiments in driving simulators. Results from this study suggest that visibility and pedestrian time-to-arrival are the most important variables for defining the earliest acceptable FCW and AEB activations. Fractional factorial design effectively compared the influence of seven factors on driver behaviour within a single experiment; however, this design did not allow in-depth data analysis. In the future, OpenDS might become a standard platform, enabling crowdsourcing and favouring repeatability across studies in traffic safety. Finally, this study advises future design and evaluation procedures (e.g. new car assessment programs) for FCW and AEB by highlighting which factors deserve further investigation and which ones do not.

Iniciacao Sexual e a Etiologia das Disfuncoes Sexuais Masculinas

A sexualidade adulta depende de um desenvolvimento sexual adequado, o que inclui uma iniciacao sexual bem ajustada e integrada a personalidade de uma pessoa. Em homens com queixas de disfuncoes sexuais a iniciacao sexual pode ser relacionada a estas disfuncoes e suas causas: organicas ou psicologicas. Objetivando estabelecer possiveis associacoes entre a iniciacao sexual do homem brasileiro sexualmente disfuncional e estas disfuncoes, estudaram-se retrospectivamente 200 pacientes homens com idade media de 42 anos, casados (68,5 por cento). A disfuncao eretil era a principal queixa (89 por cento), 8 por cento queixavam-se de ejaculacao prematura e 3 por cento outras queixas de inadequacao sexual. A iniciacao sexual deu-se aos 15 anos, sendo que 5 pacientes com causas psicologicas para a disfuncao permaneciam virgens (idades entre 18 e 24 anos). A etiologia psicologica foi encontrada para 70 por cento, a organica para 18 por cento e eram mistas em 12 por cento da amostra. A iniciacao com prostitutas ocorreu em 52 por cento da amostra, sendo maior entre os organogenicos (69 por cento). Os pacientes que nao se lembravam da primeira relacao (3 por cento) tinham origem psicologica para a disfuncao queixada. Os pacientes psicogenicos tiveram maior distribuicao de parceiras sexuais para a primeira relacao do que tinham origm organica para a disfuncao. A iniciacao sexual masculina com prostitutas e comum a populacao brasileira, mas o homem que ja apresenta personalidade fragil tem dificuldades em enquadrar-se nas exigencias sociais e necessita buscar outras fontes para a satisfacao sexual. Portanto, os homens com origens psicologicas para a disfuncao sexual tendem a buscar menos a prostituta, o que talvez venha a explicar a maior incidencia tambem de mas lembrancas da primeira relacao sexual, geralmente vivenciadas com medo e angustia e ate mesmo medo, evoluindo para inseguranca e preocupacao excessiva com a fantasia do prazer orgasmico da parceira, e a manuntencao da masculinidade.