Scirocco Central

I have retrofitted the RNS 510 to my Roc and overall am very pleased with it. I have noticed however that it's estimation of the time it will take for a trip is way out. For example yesterday we went on a 93 mile trip to Cornwall from Devon mostly on the A30. The RNS estimated the journey time as 2 hours 22 mins. It actually took only 1 hour 30 mins driving pretty leisurely as we were enjoying the views! The only settings I can find for this are to set average speed for route calc as slow,medium or fast and this was already set to fast. In other sat-navs you are able to set the actual speed to use for each different type of road, is this possible anywhere in the RNS? I have downloaded a copy of the manual but one of the pages referred to for route settings (p66) is missing from the pdf file version. I have been into the "secret" menu aswell and can't see anything to do with route calculation.

My old Tomtom used to be pretty accurate on route times once the road speeds were set sensibly, but the RNS seems to think I am cycling not driving!

TomTom is the most accurate on routing and journey times since it introduced IQ routing. The margin is massive. Other systems have no way to discriminate between declassified roads. Around here, there are declassified roads where 100mph is safe and 15mph is reckless and without the average vehicle speed measurement you get with IQ routing, calculations of distance (and fastest routes) will be way off.

If you've been using TomTom spookily accurate traffic data via a 3G data connection, the TMC stuff in the RNS is going to be a big disappointment too. Guiding you round traffic jams that aren't there adds to journey times, Inaccurate traffic information is worse than none.

I know what you are saying but I don't think that declassified road speeds were the problem in this case. 90% of that journey was on the A30 which is dual carriageway. Judging by the estimated journey time, the RNS thought I would be doing about 40mph on it when if fact it was easy to cruise at 70mph or more. What I want to know is if there is a way of manually setting the speed used for route calculations for different types of road in the RNS. This seems important as it must effect the routing too. If it's calculations assume only 40mph on a dual carriageway, it wouldn't prioritise that type of road over a single carriageway road that was marginally shorter in distance.

The journey time does adjust as the journey progresses and the 'accuracy' can be altered on the 'Navigation' menu to either low medium or high ( I think because there is the facility to change it but I never have )

nd10 wrote:The journey time does adjust as the journey progresses and the 'accuracy' can be altered on the 'Navigation' menu to either low medium or high ( I think because there is the facility to change it but I never have )

Yes, I know the journey time adjusts as you progress, but that is no help in estimating how long the journey will take in the first place. In my example is was out by over 50% in the first place. As I said in my original post I already have the average speed set to fast in the settings.

What I wanted to know was if there was a more sophisticated way of setting average speeds for individual road types. I guess there probably isn't as someone here would know about it if you could!

As a test, I have just changed the average speed to slow and put in the same route. It now reckons the 93 miles would then take 2hrs 55 mins! That is not much more than 30mph average on mostly dual carriageway with a 70 limit.

So to the RNS, fast is averaging 40 mph and slow is 30 mph, was it programmed for a little old man in a pork pie hat, driving a Rover 213?!!