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How much can you trust that data? My car tell me what the speed limit is by using a database and reading signs. On my commute to work there is a part where it t

How much can you trust that data? My car tell me what the speed limit is by using a database and reading signs. On my commute to work there is a part where it tell me the speed limit is 5km/h when it actually is 80km/h and another place where it for a short bit shows the limit as 80km/h where the correct is 30km/h

leokennis 7y ago
In The Netherlansds (and probably other places), many roads have a different maximum speed between 07:00-19:00 and 19:00-07:00.
- t0mas88 7y ago
  Both Netherlands and Germany have these time based speeds on a lot of highways where the special case is in text underneath the sign. BMW handles it if the navigation database is up to date. At least on the A2 in the Netherlands, which has the 06:00 to 19:00 changes between 100 and 130. It also understands temporary changes for roadworks, but gets it wrong when a roadwork/temporary sign has an exception like "when road is wet" That tells me the camera only understands the main sign and then the navigation database tells it about exceptions / special cases. Nice as a small reminder on your screen, but I wouldn't trust it to self drive based on that data.
joshvm 7y ago
Neither is ideal. But you should use what information you have. There is still no excuse for making a decision like 85 in a 35. Worst case this should be a disengage or the car could defer to you - eg visual warning on the dash "speed limit unclear, override?" In the UK smart motorways can vary from 30mph to 70mph according to traffic. This can change within minutes and obviously cannot be in databases. So this is a good case for sign recognition. In theory though, there is some network that's updating the speed limits and there's no technical reason why that couldn't be a public information service (maybe it already is). Then you have the sibling comments - speed limits which are time based. I would imagine this is country specific and is, mostly, a matter of public record. But would you trust CV to recognise text on a sign with specific hours? I don't know how complex the signage is, but trying to use ML for this seems absurdly wasteful of resources. Finally you have other information - how fast are the cars around you travelling? Have you detected an obstruction on the road (eg cones)? Is the weather inclement and therefore you should drive more slowly, etc. I would imaging that if self driving cars become ubiquitous there will eventually be a system for real time speed limit determination, whether that's some kind of wireless beacon at regular intervals or an online database that's kept up to date I don't know.
- rypskar 7y ago
  How is the accuracy of sign recognition on the LED signs stating the current speed limit? My experience is that it is not so good, maybe other cars are better at reading LED signs. For the car to react according to how other cars drive, you need to have other cars on the road at the same time. I have a narrow gravel road where the limit is 30km/h but safe driving is between 10 and 20, but my car tell the limit is 50km/h. It can be weeks without me seeing other cars on that road at the same time as me. Some mornings during the winter I can drive because I know where the road is, not because all of it is visible. Good luck having an autopilot doing that
  - joshvm 7y ago
    Well, quite. But again this is all supplementary information. The car should have a basic idea of the speed limit from a database and it should adjust as appropriate. Similarly the car should be able to identify road surface conditions and also how much power it's needing to put in to achieve a set speed. If it's identified that traction is being lost over gravel, then it should reduce power. Equally the autopilot should consider visibility. There are plenty of roads that are national speed limit and you'd be insane to drive at 60 on them due to blind or extremely tight corners. But with LEDs this seems like massively over-engineering the problem. Why use computer vision when you can potentially broker a deal with the highways agency to get live speed limits on a particular stretch of highway?

leokennis 7y ago

In The Netherlansds (and probably other places), many roads have a different maximum speed between 07:00-19:00 and 19:00-07:00.

t0mas88 7y ago
Both Netherlands and Germany have these time based speeds on a lot of highways where the special case is in text underneath the sign. BMW handles it if the navigation database is up to date. At least on the A2 in the Netherlands, which has the 06:00 to 19:00 changes between 100 and 130. It also understands temporary changes for roadworks, but gets it wrong when a roadwork/temporary sign has an exception like "when road is wet" That tells me the camera only understands the main sign and then the navigation database tells it about exceptions / special cases. Nice as a small reminder on your screen, but I wouldn't trust it to self drive based on that data.

joshvm 7y ago

Neither is ideal. But you should use what information you have. There is still no excuse for making a decision like 85 in a 35. Worst case this should be a disengage or the car could defer to you - eg visual warning on the dash "speed limit unclear, override?" In the UK smart motorways can vary from 30mph to 70mph according to traffic. This can change within minutes and obviously cannot be in databases. So this is a good case for sign recognition. In theory though, there is some network that's updating the speed limits and there's no technical reason why that couldn't be a public information service (maybe it already is). Then you have the sibling comments - speed limits which are time based. I would imagine this is country specific and is, mostly, a matter of public record. But would you trust CV to recognise text on a sign with specific hours? I don't know how complex the signage is, but trying to use ML for this seems absurdly wasteful of resources. Finally you have other information - how fast are the cars around you travelling? Have you detected an obstruction on the road (eg cones)? Is the weather inclement and therefore you should drive more slowly, etc. I would imaging that if self driving cars become ubiquitous there will eventually be a system for real time speed limit determination, whether that's some kind of wireless beacon at regular intervals or an online database that's kept up to date I don't know.

rypskar 7y ago
How is the accuracy of sign recognition on the LED signs stating the current speed limit? My experience is that it is not so good, maybe other cars are better at reading LED signs. For the car to react according to how other cars drive, you need to have other cars on the road at the same time. I have a narrow gravel road where the limit is 30km/h but safe driving is between 10 and 20, but my car tell the limit is 50km/h. It can be weeks without me seeing other cars on that road at the same time as me. Some mornings during the winter I can drive because I know where the road is, not because all of it is visible. Good luck having an autopilot doing that
- joshvm 7y ago
  Well, quite. But again this is all supplementary information. The car should have a basic idea of the speed limit from a database and it should adjust as appropriate. Similarly the car should be able to identify road surface conditions and also how much power it's needing to put in to achieve a set speed. If it's identified that traction is being lost over gravel, then it should reduce power. Equally the autopilot should consider visibility. There are plenty of roads that are national speed limit and you'd be insane to drive at 60 on them due to blind or extremely tight corners. But with LEDs this seems like massively over-engineering the problem. Why use computer vision when you can potentially broker a deal with the highways agency to get live speed limits on a particular stretch of highway?