What are safe speeds?

Answer

Safety is an important criterion for determining speed limits. Which speed is safe depends on the road function – and consequently – on the traffic mix and the nature of possible conflicts. Among other things, the Sustainable Safety principle (Bio)mechanics ([24]; see SWOV fact sheet Sustainable Road Safety) implies that traffic flows that use the same space should differ in speed, direction, and mass as little as possible. If differences in direction (at intersections for instance) and mass (for example when motorised traffic and pedestrians interact) do occur, driving speed should be low to realise sufficient safety. The so-called stopping sight distance, i.e. the distance required to observe and recognise an object on the road, and to make the vehicle stop on time, also determines which speed is safe, as does the safety of the verges.

These general principles have resulted in an overview of safe speeds for different circumstances (Table 2).

  

Potential conflicts and requirements associated with

Safe speed (km/h)

Possible conflicts with vulnerable road users in home zones 

(no foot paths and pedestrians using the carriageway)

15

 

Possible conflicts with vulnerable road users on roads and at intersections, including situations with bike lanes or advisory bike lanes

30 

No conflicts with vulnerable road users, except with helmet-protected riders of motorised two-wheelers (mopeds on the carriageway). Possible right-angle conflicts between motorised vehicles, possible frontal conflicts between motorised vehicles. Stopping sight distance ≥ 47 m

50 

No conflicts with vulnerable road users 

No right-angle conflicts between motorised vehicles, possible frontal conflicts between motorised vehicles

Obstacles shielded or obstacle-free zone ≥ 2.5 m, (semi)hard shoulder

Stopping sight distance ≥ 64 m

60 

No conflicts with vulnerable road users 

No right-angle conflicts between motorised vehicles, possible frontal conflicts between motorised vehicles

Obstacles shielded or obstacle-free zone ≥ 4.5 m, (semi)hard shoulder

Stopping sight distance ≥ 82 m

70 

No conflicts with vulnerable road users 

No right-angle or frontal conflicts between motorised vehicles

Obstacles shielded or obstacle-free zone ≥ 6 m, (semi)hard shoulder

Stopping sight distance ≥ 105 m

80 

No conflicts with vulnerable road users

No right-angle or frontal conflicts between motorised vehicles

Obstacles shielded or obstacle-free zone ≥ 10 m, hard shoulder 

Stopping sight distance ≥ 170 m

100 

No conflicts with vulnerable road users

No right-angle or frontal conflicts between motorised vehicles

Obstacles shielded or obstacle-free zone ≥ 13 m, hard shoulder 

Stopping sight distance ≥ 260 m

120 

No conflicts with vulnerable road users

No right-angle or frontal conflicts between motorised vehicles

Obstacles shielded or obstacle-free zone ≥ 14.5 m, hard shoulder

Stopping sight distance ≥ 315 m

130 

Table 2. Elaboration of ‘safe speed limits’. Differences with the row above are indicated in bold (Source: SWOV fact sheet Sustainable Road Safety).

Part of fact sheet

Speed and speed management

If the average speed on a road increases, crash risk also increases, as does the risk of a serious outcome.

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