[OSM-dev] [Routing] webservice to collect traffic messages

Tom Evans tom_evans_a at yahoo.co.uk
Tue Apr 21 10:03:37 BST 2009


marcus.wolschon at googlemail.com wrote:
> On Tue, 21 Apr 2009 09:17:36 +0100, Tom Evans <tom_evans_a at yahoo.co.uk>
> wrote:
>> marcus.wolschon at googlemail.com wrote:
>>> Why would anyone be interested in when the event started?
>>> It's there, it will be there when you get there so it's
>>> to be used in the metric.
>> Most traffic congestion doesn't operate to an accurate timetable? 
>> Typically, you have observations of the congestion (at a known 
>> time), and an estimated (i.e. made up) duration.
> 
> Correct and if a new estimate becomes known or the cancellation
> of the event is broadcast it gets updated.

Yes, I was just implying it was a shame to throw away the one piece 
of known good information and send the guessed bit instead.

>> For the few events which are predictable, you'd want to take 
>> advantage of that and broadcast the prediction. But without implying 
>> the event has already started.  Unless I'm missing something, you 
>> can't do that with just expiration date.  Just a thought.
> 
> So you mean expected events?
> I did not think about these before. Do you know any sources
> where we may actually get such data?

Rush hour is a bit of a broad one, but there are definitely 
particular hotspots that become much worse than the rest then.  I've 
also seen occasional warning of queueing for a big event, which 
should presumably be known in advance.  Also some motorway roadworks 
have a scheduled start time.  I don't think it's the common case by 
any means, but it would be a shame to encode the scheme such that 
they could never be described.

> This is becoming more complicated then I expected.

For that reason alone I like the name-value pairs you put in.  My 
instinct is to try and push everything that isn't essential and a 
fixed byte count into that, but I can't think where I'm getting that 
idea from...

Tom





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