CityCyclingEdinburgh was launched on the 27th of October 2009 as "an experiment".
IT’S TRUE!
CCE is 15years old!
Well done to ALL posters
It soon became useful and entertaining. There are regular posters, people who add useful info occasionally and plenty more who drop by to watch. That's fine. If you want to add news/comments it's easy to register and become a member.
RULES No personal insults. No swearing.
@acsimpson - absolutely.. well said.
I have an OBD2 bluetooth device which can be paired to the torque pro app - for many cars I believe you can accurately calculate the amount of fuel used on a trip, and use GPS to accurately tell speed. Anyone's welcome to borrow it if they want to have a go at replicating Blueth's results. (I'll also have a go, but I need a different device as I have an ancient KWP OBD2 protocol)
@blueth.
I'm interested in your experiment and think there is a few flaws in the setup. I am guessing that you are relying on your car to tell you how much fuel you are consuming. This will in turn be using your car's own speed/mileage reading but meanwhile you are making your own measure of speed which somewhat negates the cars reading.
You are also assuming that the car is accurately measuring fuel consumption while outright stating that it is inaccurate when it measures speed.
There is a large amount of education needed before an average car buyer is aware that there is more to emissions than CO2.
Not just the average punter but the powers that be too. "Road Tax" is currently modelled on a fanciful interpretation of average CO2 emissions of any given vehicle.
Were you to also add in a NOx and particulate component to the taxation model, all those "clean" diesels (sold under various technology subbrands preceded by the greenwashing words like eco-, i, blue, clean-) might prove slightly more expensive in their running costs.
I'd also like vehicle length, weight, power and noise output to be added in to the taxation matrix. Hopefully we could do something to discourage the executive saloon driving classes on their migration towards monstrous hybrid SUVs.
You are also assuming that the car is accurately measuring fuel consumption
I reckon they are extremely inaccurate at very low fuel rates.
On my Mazda 6 it even reads 0 (litres per 100miles!) when the car is idling and stationary. It should read infinity! This results in a very misleading average fuel consumption reading, since it is effectively ignoring all the fuel wasted while I'm sat in a queue not moving anywhere.
Nice green-washing Mazda
@blueth "The facts? Travelling at a steady 20 used one third more fuel than at 30."
Driving at a constant 20mph/30mph the overheads* are pretty much the same. The difference in engine efficiency is probably marginal. I'd suspect the actual amount of fuel going into the engine (per unit time) in each case is very similar.
If fuel was being used at exactly the same rate (per unit time) for both speeds, the fuel consumption (MPG) at 30mph will be 50% higher than at 20pmh. (you have to drive for 50% longer in time at 20mph and burn 50% more fuel for the same distance)
If it required 1.5 times more fuel to cruise at 30mph than 20mph then the MPG figures would be equal at each speed.
I suspect the reality is that 30pmh requires a small amount more fuel (per unit time) - about 1.1 times more would give the difference in MPG you see.
*A good engine running in its sweet spot in terms of RPM and load may be 30% efficient - 30% of the energy extracted from burning fuel is converted into potentially useful work. The efficiency varies with RPM/load. From that 25%, you can take off transmission losses, friction, air resistance, etc.
Personally I use the simple method of making a note of how far I've travelled since the last full tank, and then note how much has to be put into the tank to replace what's been used.
The car's reported average mpg can be considerably off in either direction (up to 20%). I suspect this is something to do with the profile of journeys, eg cold starts, short or long trips, temperature, humidity, etc.
This only really works to illustrate the unreliability of what the car reports. It's not so useful in measuring the 20 vs 30 fuel consumption, because I'd have to drive quite a long way at 20mph to use enough fuel to remain statistically accurate.
However, with respect to pollution, the 20mph vs 30mph argument about fuel consumption is missing the point. As various people here have pointed out, the bulk of per-car pollution comes when engines are cold, i.e. in the first 5 miles. Using pollution reduction as an argument in favour of 20mph is just rearranging the deckchairs on the Titanic. Cold-engine pollution will continue to hugely outweigh the 20-or-30 difference.
(this ignores the predicted traffic-smoothing effect of 20mph limits which may have a separate beneficial effect on overall fuel consumption)
"However, with respect to pollution, the 20mph vs 30mph argument about fuel consumption is missing the point."
Couldn't agree more. 20mph limits might convince people they don't need to drive for journeys <5miles, which is really where the big gains are to be made. Especially given:
"As various people here have pointed out, the bulk of per-car pollution comes when engines are cold, i.e. in the first 5 miles."
@Snowy - you are correct of course, and I entirely agree. Forgive me for being pedantic about a fairly inconsequential point, but I object to blanket statements being made about fuel consumption and rpm as they are based on what I believe to be incorrect assumptions, which is why I questioned it. I think you're right that this line of argument is largely irrelevant given what you say about cold engines etc.... edd1e_h and urchaidh have also pointed out that emissions difference at a constant 20 vs 30 constant pale into insignificance compared to accelerating to 20 vs 30.
"The Reducer" - love it! Maybe someone can do a full-on Marvel style version of this?
Nice!
Starts on Sunday!
Keep your ears peeled for the sound of exploding gearboxes. Edinburgh Spotlight's FB post attracted some particularly nerkish stuff. How anyone in the history of automotive travel has ever managed to accelerate through 20mph to higher speeds before is a mystery.
Oh FFS; from the BBC "If cyclists are going too fast and unable to stop properly they would be charged with dangerous or careless cycling." That'll be the charge code next to 'permit a dog in the road'
Sounds pretty common sense, doesn't it? Bikes aren't fitted with speedometers so rather than holding us to a fixed limit, they just basically say "keep to a safe speed for the conditions."
Answers the EEN-style "BUT WILL THIS APPLY TO BIKES??" questions, at least.
Keep your ears peeled for the sound of exploding gearboxes.
I doubt that will happen. Judging by the apoplexy amongst commenters, I'd look out for exploding superficial temporal arteries.
I have seen my first 20 mph sign entering curriehill looks a bit smaller than the 30 that was there before
.
Scotstoun Road in S Queensferry goes to 20 on Sunday as well. Good news to counteract the increased traffic to the new housing estate.
BIG UP THE REDUCE-AH !
Looking at the map for this, there are some pretty strange decisions - e.g. East Fettes Avenue, Polwarth Terrace.
"
Call me cynical
5:05 PM on 30/07/2016
I ask once again why the roads in the city with the highest rates of injuries and fatalities are not included in the 20 mph limit ? If, as Hinds always claims it's about safety then surely the most dangerous roads should be reduced to 20 mph first, and if not then why not if its all about safety allegedly. In this same edition there is a report that the A90 is one of the most dangerous roads in Scotland, not just Edinburgh, so if Hinds has not reduced this road to 20 mph then it blows her talk of "for safety" out of the water and points to another agenda by the useless woman.
"
20mph in Balerno, Ratho etc too as from tomorrow so far only heard voices in favour.
"
31/07/2016 8:54 PM
stantheman
Who authorised the 20 mph signs in Balerno . W Edinburgh- nowhere near the city centre - this is clearly illegal expenditure and I shall be alerting the council auditor
"
http://www.edinburghnews.scotsman.com/news/edinburgh-s-20mph-speed-limit-enforced-1-4190201
(The headline has been changed, but nothing about enforcement!)
Ooh, comments there best avoided. Foaming and frothing. No consultation? Maybe we are just really well informed here? Seems like the 20mph roll out has been discussed for months?
Balerno and Ratho are zone 1 clearly on the map. The key on the map also suggests 1 means first not centre. Two means second etc.
Cycling round Fife yesterday most villages went down to 20 mph from faster speeds so moving from one Zone to another should not be beyond capabilities.??
"should not be beyond capabilities"
That's a lot of faith in "should"...
@gembo
"Ooh, comments there best avoided."
I don't know, I quite liked this one:
"It will be interest to be the increase in road accidents and CASUALTIES over the next few years."
I felt it summed up the logic of the pro-speeding case quite nicely.
@gibbo - don't forget that that comment was prefaced by "UTTER MADNESS" - which for me added considerably to its gravitas.
@gibbo, I read that one but I could not see how it made any sense, which as you say sums up the logic of EEN posters? Or I think poster with various handles.
Went down Currie fm library which is still 30mph to the station the whole stretch is 20mph which will be hard for some though a lot of drivers get it as the school is half way down. Back to 30 mph after the train station.
this will be on Call Kaye today. discussion about fines v. courses. maybe more.
they called me up to see if I'd be willing to go on, then talked to me and decided I was too 'reasonable' and they wanted someone to take sides more!
they're trying to generate a debate about the existing fines v. the sorts of 'remedial' courses that are offered down south. I said fines seemed good as a deterrant (maybe, for some) but that anecdotal evidence (which I have reported here before), was that courses very effective.
You must log in to post.
Cycling in Edinburgh Flickr group
Video embedded using Easy Video Embed plugin
posts