How to do a cycle traffic survey

Adnepos
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Joined: 15 Jun 2016, 1:47pm

How to do a cycle traffic survey

Postby Adnepos » 23 Aug 2020, 1:00pm

My council says it has done a survey at a local junction (BP Garage Roundabout on the A10 near Ely) and report only 17 cycle movements in a day.

I don't believe the number (I've been waiting for a Freedom of Information Request report for 3 months...) and plan to do a count myself -well, with help from others.

Is there some protocol that we should follow?

I've looked online and not found anything helpful.

Jdsk
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Joined: 5 Mar 2019, 5:42pm

Re: How to do a cycle traffic survey

Postby Jdsk » 23 Aug 2020, 2:15pm

It's 20 y old, but if you want to do this yourself have a look at:
https://trl.co.uk/sites/default/files/TRL395.pdf

Jonathan

atlas_shrugged
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Re: How to do a cycle traffic survey

Postby atlas_shrugged » 23 Aug 2020, 7:00pm

Contact the SaveOurCycleStreet people who did a survey on Adams Road, Cambridge. They found the Cambridgeshire supplied statistics way out and much less than the figure they measured when they did their own count. They got at least a couple of counting gadgets that you click for their own survey. The main organisers live on Adams Road.

You could also use a time lapse camera if you can mount this where it will not be stolen.

drossall
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Re: How to do a cycle traffic survey

Postby drossall » 23 Aug 2020, 10:55pm

I'm no expert, and I don't know the junction. But I'd have thought there's pretty-obviously something around thinking about what are likely to be the busy times of day, and ensuring that measurements neither underestimate (by missing these) nor over-estimate (by focusing on them).

The other thing is the conclusions being drawn. Depends what you really want to know - how many bikes actually go through now, or how many would if a particular junction were less intimidating.

FatBat
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Re: How to do a cycle traffic survey

Postby FatBat » 25 Aug 2020, 9:52am

In my previous career, I commissioned and undertook plenty of traffic surveys. Accurately counting bicycles is relatively straight-forward on a bike-path, or similar, where bikes are the only vehicles. There are automatic counters available that can do this. Counting bicycles in a mixed traffic stream is much more difficult to do automatically. In general, the only way to do such counts is to have people at the roadside manually recording vehicles as they pass, or to install a CCTV camera and then review the footage later.

The problem with doing manual counts is that they can only cover a relatively short period - an automatic counter can be put down and left for a few weeks, but I've only ever known manual counts cover a single day. So, the question then is - what day should you do a manual count on? In general, traffic levels vary from day-to-day, week-to-week and month-to-month, and bicycle traffic levels are much more variable than motorised traffic levels. If you do a count on a particular day, you have to bear in mind that your count may be lower or higher than a "typical" day. Of course, you have no way of knowing what a typical day is. Generally, you should avoid school holidays, weekends and bank holidays. Given the circumstances we're in at the moment, I'd say there is no such thing as a typical day, and any counts undertaken during the pandemic are unlikely to represent typical conditions. But, that hasn't stopped my local council from putting down loads of automatic counters all around the local area.

For the location in question, the junction looks too big for one person to observe all the arms at the same time. Ideally, you'd have a person on each arm, counting bikes as they pass. To avoid double-counting, they should only count bikes entering the roundabout, not leaving it. Using a hand-tally counter can help, but if you are only counting bikes, you probably won't need them.

Then, you have to decide how long to count for. In general, manual counts are done over a 12-hour period (7am to 7pm) or a 16-hour period (6am to 10pm). I can't imagine you'd get many volunteers to stand around for such lengths of time! You could concentrate on the "peak" periods - whilst these periods are well defined for motorised traffic, they aren't so clear for non-motorised traffic.

As an aside, one of my previous employers undertook a full traffic survey on a road I used to commute on - when the results came in, the count of bicycles on that road was recorded as zero - even though I had cycled past, following another a chap on a bike, whilst the survey was ongoing. So, I always take the results of such surveys with a pinch of salt.

Hope this helps.

Adnepos
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Joined: 15 Jun 2016, 1:47pm

Re: How to do a cycle traffic survey

Postby Adnepos » 26 Aug 2020, 2:55pm

drossall wrote:I'm no expert, and I don't know the junction. But I'd have thought there's pretty-obviously something around thinking about what are likely to be the busy times of day, and ensuring that measurements neither underestimate (by missing these) nor over-estimate (by focusing on them).

The other thing is the conclusions being drawn. Depends what you really want to know - how many bikes actually go through now, or how many would if a particular junction were less intimidating.

The objective is to show the council number is an order of magnitude too low. So we plan a single survey, 7am-7pm, with information aggregated by the hour, for each of the two directions we are interested in. A count doesn't help much assess suppressed demand, although counting those on the road versus those on the shared use path might give some ammunition.

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mjr
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Re: How to do a cycle traffic survey

Postby mjr » 26 Aug 2020, 3:18pm

The questions about when to count and how many counts to make are covered in that TRL395 that Jdsk linked, particularly section 3.1.

Doing one day-long count risks being accused of having picked a freak day.
MJR, mostly pedalling 3-speed roadsters. KL+West Norfolk BUG incl social easy rides http://www.klwnbug.co.uk
All the above is CC-By-SA and no other implied copyright license to Cycle magazine.

basingstoke123
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Re: How to do a cycle traffic survey

Postby basingstoke123 » 30 Aug 2020, 10:19pm

Is the aim to get a more accurate count of cyclists on this roundabout, or to show that the council's figure is unreliable and too low? If the figures are much higher, then it should not take very long to observe 10 cyclists using the junction. While this will not give an accurate estimate of daily use, it would show that the 17 per day was wrong.

Did the council's figures include cyclists using the pavement (which, from Google Maps appears to be a bit of Cycle Route Along Pavement)?

As roundabouts are the junctions most feared and disliked by cyclists, you would expect cycling at a roundabout to be lower than expected (if that makes sense!) So perhaps you should also be measuring cycling along and nearby alternative routes, which might be used as a detour.

You would never justify building a bridge based on how many cars crossed a deep ford.