During what condition is road user reaction time typically longest?

Road user reaction time is typically longest in foggy conditions due to several factors associated with reduced visibility. When fog is present, visibility is significantly compromised, which impacts a driver's ability to see other vehicles, pedestrians, and signals. The uncertainty created by fog can cause drivers to be more cautious and take longer to make decisions regarding speed and direction, subsequently increasing reaction time.

In fog, drivers may also struggle to gauge distances accurately, leading to delayed responses to changes in the driving environment. This is compounded by the potential for unexpected obstacles or changes in traffic conditions, all of which necessitate a more measured and slower response.

In contrast, clear weather generally allows for quick recognition of hazards, while rainy weather may introduce hydroplaning risks that could affect reactions but not to the extent of fog. Snowy conditions can also lead to slower responses, but the major issue here is often related to vehicle control rather than visibility. Thus, foggy conditions notably stand out as the scenario where road user reaction time is at its longest, primarily due to the significant reduction in visibility and the consequent cautious approach drivers must adopt.