Abstract
The speed-reducing effect of speed humps during darkness is important to ensure a consistent speed reduction and a decreased probability of accidents during darkness. This study examined the effects of speed humps, compared with a control location, on a residential road in Sweden with light-emitting diode (LED) street lighting and a 30 km/h posted speed limit. Hypotheses tested were that: (I) vehicle speed is higher during daylight than in darkness; (II) speed at speed humps is lower than at control locations during both daylight and darkness; (III) speed at humps is higher during daylight; (IV) vehicle speed at humps is lower when luminance or visibility of the humps is greater; and, (V) the road environment of speed humps is perceived as being similar by drivers. The results showed that vehicle speed at the control location was negligibly higher (+0.3 km/h) during daylight than in darkness. Speed humps reduced driving speed by 20% when compared with the posted speed limit and the effect was not significantly different between daylight and darkness. Speed reduction for the three speed humps varied between 9% and 29% as compared with the posted speed limit. In this study, the LED road lighting that was placed directly above or in front of the hump achieved the highest luminance. This study could not reveal any significant differences in vehicle speed attributable to light conditions per se.
Highlights
Since the establishment of the new safety paradigm (Vision Zero) in Sweden in 1997, traffic safety policy has focused on road redesign, lower vehicle speed, and managing the kinetic energy from collisions in such a way that fatalities and serious injuries are zero (e.g., [1])
This study showed that vehicle speed at the control location was negligibly higher in daylight than during the hours of darkness, but that the speed-reducing effect of humps was similar between daylight and darkness
No speed radar can accurately differentiate between speeds that differ by only 0.3 km/h, which was the difference that we found between daylight and darkness, so the speed difference can be considered to be negligible
Summary
Since the establishment of the new safety paradigm (Vision Zero) in Sweden in 1997, traffic safety policy has focused on road redesign, lower vehicle speed, and managing the kinetic energy from collisions in such a way that fatalities and serious injuries are zero (e.g., [1]). Much effort has been devoted to increasing safety for all of the categories of road users. One of the main factors is reducing vehicle speed, especially in potential conflict areas between vehicles and vulnerable road users (i.e., pedestrians, cyclists, joggers). Vulnerable road users should not be exposed to vehicular traffic driving at speeds exceeding 30 km/h. In Sweden, roads with vulnerable road users have a maximum speed limit of 30 km/h and commonly include additional speed-reducing designs, for example, narrow lanes, speed humps, or speed bumps to further reduce vehicle speeds to below 30 km/h
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