Intelligent Speed limiter is stupid!

[keithr]

When I read that the Honda e had an Intelligent Speed Limiter, where it would automatically set the speed limiter to the speed limit that it saw using the traffic sign recognition system, I thought that was a great idea. It would be reassuring to use it so that it would prevent you from exceeding the speed limits and therefore prevent you getting any speeding tickets. It seemed like a genuinely useful feature. However, it seems the system is flawed and rendered virtually useless by a stupid design decision!

In the Nissan LEAF that I had it also had speed limit sign recognition, and it would sensibly and logically always display the last speed limit that it saw. It would also remember the speed limit when you turn the car off, so it starts up with the same speed limit (very sensible!). However, it seems the Honda e doesn't do that. I noticed while driving around town that after getting to the end of a road, at a junction or roundabout, and turning left or right into a different road, that if there are no speed limit signs along that road then instead of continuing to display the same speed limit sign it instead gives up and just displays the "I've no idea what the speed limit is" sign (a grey circle with three dashes in it).

So I checked in the Owner's Manual traffic sign recognition system section and it says:

The sign icon will be displayed until the vehicle reaches a predetermined time and distance.

The sign icon also may switch to another one, or disappear when:
•The end of speed limit or other designated limit is detected.
•Your vehicle enters/exists motorway or highway.
•You make a turn with a turn signal at an intersection

So even if you don't indicate in order to preserve the speed limit indication, it will still time out after a while and not display the 30mph limit!

And likewise in the ISL section:

The speed limitation function and warning function may switch to pause if there is no speed limit sign in the screen of the traffic sign recognition system when:
•The end of speed limit or other designated limit is detected.
•Your vehicle enters/exits motorway or highway.
•You make a turn with a turn signal to change direction at an intersection.

So it has been designed to work that way. That is so stupid! The speed limit in town (built-up areas with street lamps) is 30mph unless otherwise indicated. We don't clutter up our roads with 30mph speed limit signs on every single road, and everyone knows that. You assume that it's a 30mph limit unless it says otherwise. Normally there would only be a 30mph sign when changing back from a different speed limit, such as 40 or 20 mph, or entering a village/town from outside the village/town. So the Nissan approach of displaying the last seen speed limit sign makes perfect sense, and Honda's approach of giving up just because you turned into another road, or because it hasn't seen a speed limit sign for a while, is stupid, and it renders the Intelligent Speed Limiter mostly useless around town, and probably only useful on a motorway. And yet they keep telling us that this is designed to be a city car!

[bogga]

Maybe in Japan they have more signs?

[keithr]

Maybe in Japan they have more signs?

But we're in the UK and the sofware has been programmed to read UK road signs. So it should also be taylored for the local conditions of each country that the car is sold in.

Another way they could improve it is the 'national speed limit applies' sign. Honda just display it on the console, but the Nissan LEAF consults the satnav to determine if the road is single or dual carriageway and then displays 60mph or 70mph as appropriate. I haven't investigated what the Honda intelligent speed limiter does in that case - does it limit speed to 60mph on a motorway, or 70mph on an A road?! I'll try to remember to check on my next drive.

[bogga]

I totally agree that the implementation is poor. The technology is great, which is more's the pity. However there is good news though, the hardware is all there, these are just software changes, so hopefully, Honda can sort out over the coming updates.

[Larbor]

To be honest, I am not always clear on the speed limit in the UK. Coming from the Netherlands where road signage is very good, it takes some time to get used to. And I consider myself a clever, adaptable human being. A computer only does what it is taught (generally).

Improving the traffic signs here in the UK would be a better job. Especially for tourists and said systems.

[milligoon]

Software needs to adapt to its environment not alter the environment to suit a cars weak points.

All these cars come with a Garmin based satnav being a longtime user I know that the database has limits for most UK roads, where the car doesn't have a fresh sign to go on then it should use the database information surely (or it would if the algorithm was any good)

[keithr]

I haven't investigated what the Honda intelligent speed limiter does in that case - does it limit speed to 60mph on a motorway, or 70mph on an A road?! I'll try to remember to check on my next drive.

Well I've been out in my car and I spent some time using the Intelligent Speed Limiter (ISL). At first it seemed better than I thought because when the 30mph speed limit sign timed out on the traffic sign recognition display, the ISL stilled displayed 30mph as its limit and it continued to limit my speed to 30mph. So far so good.

However, later it was indicating and limiting to 30mph but when I made a right turn the 30mph display very quickly turned to the unknown speed limit icon and the ISL speed limit went to 4 dashes. When it displays those 4 dashes it is no longer limiting your speed, which I confirmed by speeding up to over 30mph. So if there had been a speed camera it wouldn't have stopped me from speeding through it.

At one point I came to a stop at some traffic lights and when I pulled away it had changed from a 30 to a 20mph speed limit display and it limited the car to 20mph, despite it still being a 30mph speed limit (I don't understand why it did that!).

When I finally entered a dual carriageway with a 70mph speed limit the car didn't spot the national speed limit sign (nor did I!) so it continued to limit me to 40mph, so I had to cancel it. Later I entered a national speed limit A road, and the traffic sign recognition displayed the national speed limit sign but the ISL just displayed 4 dashes again, which it likewise did on a dual carriageway. So the ISL won't limit your speed when it sees a national speed limit sign (the manual does say "The speed limitation function and warning function may switch to pause if: Your vehicle enters/exits motorway or highway").

I got the impression that my economy (or power consumption) was worse while using the speed limiter, but I couldn't be sure. When entering a 40mph zone from a 60mph zone it kept beeping and flashing the indicated limited speed display while it slowed the car down with regen - it didn't feel like it was applying the brakes as well but I couldn't be sure.

So the ISL is of some use but it most definitely cannot be relied upon. At best you can leave it in ISL mode but with no speed limit set, and when approaching a speed camera press the Set button to limit your speed through the camera zone (but you'll need to make sure it's correctly spotted the speed limit first!).

[Larbor]

Software needs to adapt to its environment not alter the environment to suit a cars weak points.

All these cars come with a Garmin based satnav being a longtime user I know that the database has limits for most UK roads, where the car doesn't have a fresh sign to go on then it should use the database information surely (or it would if the algorithm was any good)

No, you should not trust sat-nav data. You should trust what can be seen outside the car. That's realtime, whereas any other system has outdated data by default, and thus cannot be 100% trusted. Honda is doing the right thing, by using visual cues.

[keithr]

At one point I came to a stop at some traffic lights and when I pulled away it had changed from a 30 to a 20mph speed limit display and it limited the car to 20mph, despite it still being a 30mph speed limit (I don't understand why it did that!).

I now understand why it changed to a recognised 20mph speed limit - although the car was wrong to do so! See the attached Google Maps photo of where I was driving. I was in the right-hand lane following the road round to the right. The car saw the 20mph signs in the side road bearing off to the left and changed the display and ISL to 20mph, but the road I was on has a 30mph speed limit!

Once again, the Nissan LEAF would get it right as it only changes its recognised speed limit when it passes a speed limit sign. I was turning to the right in front of the signs and did not pass them, so the car should not have interpreted those signs as the new speed limit.

[Larbor]

Only 1 way to find out: test it with a LEAF at the same place.