speeding offences

[ian]

Here's something few people know about.

Lets say the speed limit on a freeway is 100 and the traffic density is high but not yet grid locked .

What is the optimum speed for the roads to transfer the maximum number of cars ?about 60km/h, but the actual "optimum" speed varies depending on the lane width, the number and size of trucks, trailer and caravans in the traffic stream, the number of traffic lanes, the spacing of entry and exit ramps and the volume of traffic entering and exiting, the horizontal curvature, the vertical grade AND the experience of the drivers -- do nearly all of them drive the route at that time every day, or is the traffic situation new to them?


The lane switchers and tailgaters that insist on trying to do the speed limit in higher traffic densities only slow things down not just for everyone else but for them as well.these people have the most negative impact when the traffic is still relatively "light" -- for peak hour conditions.

If I can find it, I'll post the plot we did a few years ago of the speed / volume data from a 80km/h road

[BobL]

about 60km/h, but the actual "optimum" speed varies depending on the lane width, the number and size of trucks, trailer and caravans in the traffic stream, the number of traffic lanes, the spacing of entry and exit ramps and the volume of traffic entering and exiting, the horizontal curvature, the vertical grade AND the experience of the drivers -- do nearly all of them drive the route at that time every day, or is the traffic situation new to them?
Yep it's complicated.


these people have the most negative impact when the traffic is still relatively "light" -- for peak hour conditions.
There ya go!


If I can find it, I'll post the plot we did a few years ago of the speed / volume data from a 80km/h road
Good

[Ari2]

Driving.... is that state of mind where everyone else is wrong...

[BobL]

Driving.... is that state of mind where everyone else is wrong...

Ever noticed how slow at reacting that driver is at the head of the queue when the light turns green?
Then the way the drivers behind dawdle and fail to keep up
They must be the main reason I'm always catching red lights! :D

[Dodgy Dovetails]

Of course, your car first has to actually make it onto the road! :hihi:

https://www.youtube.com/watch?v=PGMUGjlV5HU

[ian]

If I can find it, I'll post the plot we did a few years ago of the speed / volume data from a 80km/h roadGoodHi Bob

Here it is

Data is from Lane 1 of a two lane access controlled road in Sydney. I better not say which one.
Each data point represents the total number of vehicles using the Lane in an hour, plotted against the average speed of those vehicles. Data was collected over 4 "normal" weeks -- i.e. no public holidays, no school holidays in the period.
The traffic stream contains a significant number of very heavy vehicles which is reflected in the relatively low maximum volume.

You can readily see the interrelation of speed, volume and transit time and how the real world data matches the "model".

[doug3030]

[QUOTE=ian;1852736]You can readily see the interrelation of speed, volume and transit time and how the real world data matches the "model"./QUOTE]

Hi Ian,

Just trying to make sure I understand your graph. The dots represent a plot of volume per hour and average speed? Does the dot, for example aligned at approximately 65 Km/hr on the vertical axis and aligned with about 700 vehicles on the horizontal axis represent a period of an hour's duration when 700 vehicles passed along the road at an average speed of 65 km/hr? Or is it longer or shorter time periods that are adjusted to vehicles per hour for consistency of data plotting? Or is it something completely different?

Doug

[BobL]

Hi Bob

Here it is


Great - thanks for that.
Good to see a real local example.
The ones I have seen have all been US or European but they are pretty similar.

[Chris Parks]

EDIT: I forgot to mention that when I was booked fo r101 in a 100 zone my "LEGAL: speedo for a pre-2006 vehicle would have been reading 97 - 98 km/hr.

ADR's to my knowledge have always specified a speedometer that reads over?? Any links to where it was otherwise??

To save any confusion the ADR's specify that the speedo must be reading more than the actual road speed within a set tolerance.

[ian]

Great - thanks for that.
Good to see a real local example.
The ones I have seen have all been US or European but they are pretty similar.thanks Bob

the important thing about that chart is that it the data represents real vehicles -- more normally the chart is expressed as passenger car units (PCUs)
PCU data is adjusted up by adding notional cars to the total vehicles by converting trucks to an "equivalent number" of cars.
The factors involved are too arcane for this discussion.

[ian]

You can readily see the interrelation of speed, volume and transit time and how the real world data matches the "model".

Hi Ian,

Just trying to make sure I understand your graph. The dots represent a plot of volume per hour and average speed? Does the dot, for example aligned at approximately 65 Km/hr on the vertical axis and aligned with about 700 vehicles on the horizontal axis represent a period of an hour's duration when 700 vehicles passed along the road at an average speed of 65 km/hr? Or is it longer or shorter time periods that are adjusted to vehicles per hour for consistency of data plotting? Or is it something completely different?

DougHi Doug

each data point represents the number of vehicles crossing the detector in 1 hour -- there are 24 records for each day each of 1 hour duration, the first starting at 1 second after mid-night and running through to 1:00AM
vehicles is the total number of VEHICLES crossing the detector in that hour.
average speed is the average speed of all vehicles crossing the detector within that hour.
Now a count of 700 vehicles in an hour could represent 500 cars and 200 trucks. Depending on a bunch of arcane factors, one big truck might be equivalent to 5 cars, so the 700 VEHICLES might be equivalent to 1500 Passenger Car Units (PCUs).
For the work we were doing at the time, grossing trucks up to PCUs wasn't necessary.

[AlexS]

Is this permitted - confusing arguments with facts??

As we all know, gut feelings and personal hobbyhorses are much more reliable.