The sign "Tunnel with length measurement in m" indicates that a tunnel is up ahead, and it specifies the length of the tunnel in meters. This sign is important for drivers as it prepares them for driving through a tunnel, which may have specific regulations regarding speed limits, lighting, and ventilation.

When approaching a tunnel, drivers should be aware of potential changes in visibility, and they should follow any posted speed limits and safety precautions. It's also advisable to ensure that all headlights are turned on before entering the tunnel for better visibility.

If you have any further questions about driving in tunnels or any related topics, feel free to ask!