Special Speed Situation Type

Definition

Specification

Advisory Speed

• These posted speeds are not the legal limit, but rather serve to warn a driver that road conditions indicate a lower speed is practical. Typically, the road condition is a curved road or a ramp but it may be due to a narrow road, narrow bridge, intersecting road, drainage dip, etc. In some cases, the advisory sign is on a different road than the one for which it applies (this can happen with ramps). In this case, the advisory speed is indicated for the road for which it is intended, even if the sign is further than 50 metres from the particular road.
• Advisory speed signs due to construction are not included.
• A speed value is applied for advisory signs.

Dependent

• This is a speed that is enforced if certain criteria are met. Examples include: School, Rain, Snow, Fog, Time Dependent, etc.
  • School: School zone signs are often placed to slow drivers before reaching an intersection where children are crossing.
  • The speed value for school zones can be based on signs that have a posted speed value or signify a specific speed based on a legal statute.
  • Time Dependent: These are speed limits that are in effect only during a specified time period. The date range corresponding to the time is indicated in the Date Time Modifier. Also, there are cases where a different speed is applicable at night. This is indicated by Dusk to Dawn.
• These are speed limits that are in effect only under specific weather conditions:
  • Rain
  • Snow
  • Fog

Speed Bumps Present

• Speed Bumps or Chicanes: This indicates that for a stretch of road, speed bumps are present or chicanes are present that effectively reduce the posted speed. A Special Speed Limit value is not indicated for Speed Bumps.
• The following situations are not considered speed bumps/chicanes:
  • rumble strips (commonly rows of raised reflectors used to warn drivers when approaching a speed change or other situation)
  • cattle grids
  • chicanes that do not effectively slow down the traffic

    Figure 1. Special Speed Situation for School Zone