Sunday, March 01, 2020

Free buses?

One thing that is absolutely clear in the battle against congestion and pollution is that modal shift away from the private car is essential.

The fundamental issue is space-efficiency. Cars are horrendously inefficient users of the precious limited space available in urban environments. It doesn't really matter what alternative mode is used - whether walking, cycling, bus, tram, or train - changing the mode is always a big win. No, self driving cars don't help, and may make matters worse. Electric cars don't help either, you still have to get the power from somewhere, and they still have significant particulate emissions.

For larger cities, trams or rail are key. There's still work to do to drive the cost down in smaller towns and cities, but things running on rail solve the particulate emissions problem. The problem is that, while efficient, they provide more transport capacity than smaller conurbations can take advantage of. In addition, it takes years to develop a rail network.

Which leaves buses. Not ideal in the long term, but available right now. How do we get people to move onto buses - and drive up ridership on public transport to justify investment in better solutions?

What about making public transport free? After all, Luxembourg has done it. Clearly adds to the attractiveness, but can we afford it?

Consider Cambridge. The city has a population of about 125,000; with the surrounding area we might consider a quarter of a million people are in scope.

Giving that many people free public transport will cost a fortune, and we can't possible afford it. Correct?

Not so fast. The MegaRider ticket is £15 for 7 days travel. Let's round that and say it's £2 per person per day. That's a charge at which the current bus service is profitable.

What's a reasonable estimate of the number of users? Not the whole quarter of a million. Pensioners already have bus passes. Some walk, some cycle, some are already close enough to a railway station. Some, for work purposes or for special needs, will be unable to use public transport. Let's say we're targetting 100,000 people 5 days a week. That's £1million a week, or £50 million a year.

OK, that's a fair amount of money to you or me. But the CAM project (Cambridge Autonomous Metro) is talking about an eye-watering cost that may reach £4billion. Instead of funding CAM, we could fund free bus travel for everyone in Cambridge for 80 years. The Greater Cambridge Partnership was talking about a £1billion investment for the City Deal. The recent A14 "upgrade" was over £1billion.

In those terms - and in terms of many of the other projects being proposed - funding free bus travel is a bargain.

We're not done yet.

Increased ridership means fuller buses, so utilization goes up. So the cost per journey goes down.

Increased ridership justifies a denser mesh with more routes, leading to greater efficiency, driving down unit costs.

Modal shift reduces congestion, cutting journey times, so you don't need as many vehicles or as many drivers to provide the same service, driving down costs even further.

Not charging means a massive reduction in boarding times, which as I've talked about before is a major contributor to delays and inefficiency.

It's not hard, within the city, to see journey times cut in half through this process. And maybe utilization can almost double. Which means that the actual cost goes from £50million a year to £20million a year. The CAM could fund that for 2 centuries.

And that's the fundamental thing. Pretty much every single transport project currently being floated costs more - often many times more - than simply making buses free. There's a downside here - providing free buses may be sufficiently successful in the short term that it could kill off the prospects for the better long term projects. But it gives us the breathing space to develop the better solutions without destroying our cities and the planet in the meantime.

And that's only covered the direct costs, ignoring the indirect benefits such as: reduced journey times and increased productivity; decreased pollution and better health giving savings for the NHS; cleaer street and a better public realm; and so on.

Perhaps we should be asking not whether we can afford to do this, but whether we can afford not to.

Tuesday, December 10, 2019

The prospect of limiting carbon emissions

I recently went to a meeting hosted by Carbon Neutral Cambridge on developing a Local Transport Plan that would get us towards being carbon neutral.

Quick summary: the measures proposed by local authorities (specifically Cambridge, but I suspect it's not that different elsewhere) won't get us even close to being carbon neutral by 2050, and likely not ever.

Given that, realistically, any hope we have of preventing the worst consequences of climate change means that we need to be carbon neutral by 2030, this is somewhat disappointing.

There was then an analysis of a fairly radical scenario, and even that struggled to just about reach carbon neutrality by 2050.

And, what's worse, both scenarios were pretty optimistic in terms of timescale and takeup of technology. The likelihood is that there will be dithering and delays, pushing it back even further.

(And there's the incorrect assumption that switching to electric vehicles will reduce carbon emissions. On its own, it won't, it requires the world to move far faster to renewables or nuclear than we are right now.)

The other thing that isn't immediately obvious is that, right now, the carbon footprint of moving people about is the same as that for moving goods about. You have to solve both.

We then broke up into focus groups. I hate this (it's just me) - the chances are that either nobody will have anything to say so you spend the time twiddling your thumbs, or there's so much you don't even scratch the surface. On this occasion, we didn't even really get started. It's a huge topic.

But our group (although we did have Peter Dawe sidetrack us with his CitiPod) thought about a couple of priority areas:
  • For people: reduce the need to travel, and the use of remote working
  • For goods: move long distance traffic to rail, and have local distribution hubs
What is clear, though, is that we need significant modal shift from current transport systems to more energy efficient ones. Yes, this means getting rid of cars in their current form. Difficult, given the rather dire state of public transport and the lack of investment in it (although they can always find a few billion to build roads to induce extra demand and cause more congestion and pollution), but necessary.

Friday, December 06, 2019

The effect of passenger boarding on bus services

We all know the saying "you wait ages for a bus, and them 3 arrive at once". But why is this?

The basic reason is simple: once a bus starts to run late, there are likely to be more passengers waiting at stops, slowing it down. Because it's running late, the bus behind it has fewer passengers waiting when it gets to stops, and catches it up. There's a strong feedback loop that drives well-separated buses further apart, and closely separated buses get pushed together.

As a passenger, I noted the characteristics of a number of journeys I took over the summer. These were during the day, so avoid the rush hour.

Very roughly, what I see is that on a 24 minute journey between home and the centre of Cambridge, we spend typically:

  • 12 min actually moving
  • 6 minutes boarding
  • 5 minutes stopped due to traffic/lights
  • 1 minute unboarding

This doesn't account for the unboarding at my destination stop (terminus).

The boarding is much higher than unboarding for the simple reason that you just get off. When you board, you have to pay, show your ticket, or may have queries.

What was also true was that the distribution of boarding times isn't simple. The majority of passengers board quickly in the 10-20s range (there are two peaks, those who've prepaid and are just showing their card or ticket, and a somewhat slower group who have to pay). However, there's a long tail: a small number of passengers have much longer than average boarding times. I've seen some take several minutes - maybe they don't know where they're going, they don't have the right change, they don't understand the system.

The traffic lights are also rather variable. If you get caught by the lights, you can get a wait of several minutes. (The junction at the Catholic church in Cambridge in particular can cause large delays.)

Unlike a train, which pulls into a station, opens its doors for a fixed time, and then goes, a bus stops as long as necessary to let its passengers on or off. This, coupled with the traffic delays, means that wait times are highly variable.

This also means that the predicted arrival times as shown on bus stops by the real time traffic displays simply can't be terribly accurate.

I knocked up a quick model of my bus journey with the observed distribution of boarding and wait times, and (as expected) it comes back with results that aren't dissimilar to the characteristics of actual journeys:
  • Just allowing for the fact that the number of passengers on the journey is random gives a variance of +/- 3 minutes
  • Allowing for the feedback of delays early in the journey causing longer queues later gives a variance of +/- 4 minutes
  • Allowing for the previous bus as well gives a variance of +/- 5 minutes
Given this variability, it's hardly surprising that adherence to the bus timetable is notional at best.

One way to deal with this is to add waits to bring the bus back in line with the timetable. (You have to add waits, you can't remove time unless you have a time machine.) And my 24-minute journey is allowed 30 minutes, so we routinely stop 2 or 3 places along the route. But having to build in this extra wait time is pure waste.

What you can also see is that if the bus were to be full (in other words, taking on 60 people) then it's not entirely unreasonable to require 15 minutes for everyone to board. Those who have stood in a queue in the city centre on a busy evening or a Saturday afternoon will have seen the buses stationary at the stop for this sort of time. Even with the slop in the schedule, it's almost impossible to keep to the timetable if the bus is full. (Especially as those tend to be times when the roads are more congested.)

What if you could reduce boarding time? This gives you a double win: less boarding time makes the journey quicker, but also gives less variability, so you need to build in less slop. It's better for passengers, who get quicker and more reliable journeys, and it's better for the bus operators who make much better utilization of their buses and drivers.

Looking at my journey just to be specific, optimization of loading could almost halve journey times and double efficiency. At busy times on short routes having a second staff member check tickets - rather than forcing the driver to do so - is obviously a win. (This doesn't have to be a conductor, who would check or sell tickets while the bus is moving after everyone has boarded. It could be an inspector at certain stops who validates tickets of those in the queue. When I was living in Toronto some of the busier bus stops were closed interchanges, you paid as you entered the system and didn't need to be checked at the point of boarding at all.)

Eliminating charges entirely would have a similar effect. People just walk on without having to stop. Again, the system is far more efficient as a result.

One of the other minor issues with buses in Cambridge is only having one door. Those wishing to board have to wait for everyone who wants to get off to do so; many other systems have separate doors allowing boarding and unboarding to operate in parallel.

The actual process of issuing tickets has improved, I think. Smart cards and contactless payments are much quicker than the old cash and paper tickets.

But what's interesting here is that improving the efficiency with which passengers board a bus does have the potential to significantly improve journey times, reliability, and the efficiency of the bus system.

Sunday, March 31, 2019

Brexit isn't S.M.A.R.T.

If you've been through an annual performance evaluation in a large company, chances are the HR department has introduced you to the notion of setting SMART goals.

For those unfamiliar with this horror, a SMART goal is:
  • Specific - you have to avoid meaningless waffle
  • Measurable - otherwise how can you prove you've achieved it
  • Attainable - there's no point trying to do something impossible
  • Relevant - the goal must match a requirement
  • Timely - you have to be able to achieve the goal within the reporting period
How does Brexit stack up against the S.M.A.R.T. scheme?

  • Specific - Brexit is vague, undefined, or has multiple definition, possibly meaning something different to every Brexit supporter. Characterized by the vacuous slogan 'Brexit means Brexit'.
  • Measurable - fails again, largely because you can't measure something that isn't even defined. But on any objective measure, Brexit fails on every single measurable test - it won't bring more sovereignty, it won't bring more trade, it won't make us richer
  • Attainable - again, you can't attain something that isn't defined, but looking at most of the individual options for Brexit, most are simply outright impossible - they're simply incompatible with international law, or violate various UK or EU treaties
  • Relevant - for most of the individual issues that people claim to be concerned about, Brexit is an irrelevance, it's UK government policy that's the cause of the problem, not EU membership
  • Timely - claims that we would have all our trade deals rolled over and ready to go have proven false, the reality has proved that any form of Brexit is neither easy nor quick, and if we go ahead with it it's going to tie up and paralyze UK politics for a decade or more
Of course, apart from being vague and unspecified, Brexit also suffers from the fundamental problem that it shouldn't be considered as an objective in its own right - Brexit isn't something you should aim to achieve, it's rather a process by which other objectives are achieved. And when you look at those other objectives - such as sovereignty, prosperity, trade, immigration - it's clear that Brexit is at best irrelevant and most likely plain incompatible with achieving those goals.

Brexit just isn't the S.M.A.R.T. thing to do.

Saturday, November 25, 2017

Left hand Park, right hand Ride

There's been a lot of controversy in Cambridge over the parking charge for our Park and Ride service.

A few years ago, the council introduced a car parking charge. To say it didn't go down well is a bit of an understatement. Locals were outraged, not only by the charge, but the pain and complexity involved in paying for it.

Recently, a plan has come about whereby the charge would be scrapped. Essentially, the Greater Cambridge Partnership would use some of its funds to ensure Cambridgeshire County Council wouldn't take such a financial hit if the charge was removed.

Now, I'm opposed to the charge, but I'm not convinced by the solution.

I regard the charge a a symptom of the dysfunctional transport system we have around Cambridge. For background, consider this Venn diagram from Edward Leigh of Smarter Cambridge Transport:

Let's be clear. That's the abridged version. It doesn't include parish councils, MPs, national government, transport operators, or many other interested parties.

Looking at the structure, is it any surprise that our transport is an inconsistent and disorganized mess? There's no evidence of joined up thinking, and essentially every transport project is a point solution blind to the wider picture.

To my mind, the parking charge is evidence of this disconnect. It shows that rather than running a Park and Ride system, we have some car parks run by the council, and a completely separate bus service run by the bus companies. That the buses actually stop at the car parks is a fortunate coincidence; the whole thing isn't part of a coherent plan.

It gets worse, as the Park and Ride system is distinct from the general bus service. Special buses, special routes, special tickets. Again, an isolated point solution that isn't run as part of a larger plan.

So while I agree that the charge is bad, I also strongly agree with Edward Leigh when he asks whether subsidising parking is the best use of £1.1m? (It's not. You're subsidising cars and a private bus company.)

So what is the answer? Ultimately, you need to get the system sorted out. We need a coherent transport infrastructure rather than everyone pulling in different directions.

To the specifics of the charge, the pain point is paying twice. It's not the direct cost, it's the extra hassle. So pay once. Either have free parking and have the bus ticket cover the cost, or pay to park and make the bus free.

A deeper question is whether the Park and Ride system is actually useful and whether alternatives such as Travel Hubs might work better; or whether it might actually make sense to run bus services to where people live so they don't have to drive at all.

But my bigger concern about the discussion of parking charges is not just that it's leading to bad answers, but that in looking at it in isolation we're ignoring the fact that we're answering the wrong question.

Tuesday, October 24, 2017

On working from home

I've been working from home for about two and a half years now, and it's been great.

My employer, Haplo, is on the far side of London. It's not that difficult to get to, but it is almost a 3 hour trip (especially once you've allowed for the erratic bus "service" to Cambridge station). Fine for occasional visits, not something I can see being viable for a daily commute, so I go down to see everyone once a month or so.

As a systems administrator, my primary responsibility is to the servers running our products. They're hosted in datacenters, so there's no difference between my being at home (or anywhere else) or in the office - I'm always remote.

I'm also part time, and don't punch a clock. There's huge thanks to Ben for allowing this flexibility, but it benefits us both - I can fit work in around my other needs, but can also take advantage of my free time to do my work outside of normal working hours, minimising any disruption to our customers.

Working from home requires discipline, of course, and isn't for everyone. But it would take a lot to persuade me back to a full-time fixed-hours office job.

I have a routine to get the day off to a flying start. We're up early, just after 6 most days. (This actually started when Hannah was home and was getting up for the early shift at Tesco's, but we've continued with it as it fits in quite well.) Breakfast, check email and go through my iPad games to allow my breakfast to go down, then off to the gym for a swim and shower. It's good for me, and provides a fixed foundation for the rest of the day.

Lunch tends to be pretty early, 12 noon. Partly because breakfast is so early, but we also tend to have an early dinner as well.

I try to eat well (lunch usually involves a bit of meat, salad, pickles), and drink mostly water - left to my own devices I would be permanently drinking coffee, which isn't such a good thing.

I've mentioned a couple of things that are important about working from home already - establishing a routine, and having discipline to avoid bad habits. I'm not slumming around in my pyjamas either - although I do avoid proper shirts, tending to usually wear a T-shirt (I have a large collection, from vendors, trade shows, and conferences).

I'm naturally a solitary person, who would happily sit in front of a computer all day and never talk to anyone. We do keep in touch throughout the day - we're rather old school, IRC being the tool of choice.

One thing I do try and do is get out of the house. Going to the gym is part of it, but there's so much more to do as well. Cambridge has lots of museums, so I'll occasionally be out at places like the Whipple or the Fitzwilliam Museum. The Fitz is great because it's free, which means you can nip in for lots of half an hour sessions and just do one gallery at a time, rather than making a major expedition out of it. There are lots of other departmental museums well worth a visit, and a rotating exhibition at the UL.

Recently, I've also managed to get along to some of the talks that are part of the Cambridge Festival of Ideas.

I try to go to a lot of technical events through Meetup too. This tends to vary a bit, one of the annoying things is that clashes seem to be rife - seemingly far more than you might expect by chance. One of my original plans was to go to the office on the days there was an evening meetup in London (which also included the monthly LOSUG meeting before that folded), but that doesn't seem to be anything like as often as I originally anticipated.

A recent thing is the Cambridge Remote Workers meetup group. It's just an excuse to get out and socialize and network, but it's also important that it's a different set of people from wider backgrounds than is normally present at the rather narrow tech meetups I otherwsie go to.

I've started to be more active in other areas - a bit of campaigning with Smarter Cambridge Transport, looking at getting involved with the Foundation Trust at Addenbrookes. That's when I'm not supping on a tasty porter at a local beer festival, of course.

Sunday, November 13, 2016

How far to the nearest bus stop?

One question that occurred to me when I attended the Rebooting the City Deal meeting was how dense the coverage of a public transport system needs to be to make it useful.

I've seen several statements along the lines of x% of Cambridge being within a 7-minute (or whatever) walk to a bus stop. But what is a reasonable walking distance?

I don't know, but I have a little data. OK, 2 data points. Where I live I have a choice of 2 bus stops. One is about 300m away, or 4 minutes. The other is about 500m with a slightly tricky crossing, or about 7 minutes. I would have no issues using the closer stop on a regular basis; the more distant one I'm not terribly happy with.

So, if we want to encourage large-scale use of public transport, I would say we want to aim for something close to the 300m mark. How does this relate to the actual distribution of distances in Cambridge?

I looked at OpenStreetMap. They have all the buildings, and bus stops. And it's open, so I can get at the data.

The good folks at BBBike make a bunch of exports of OSM data available. This includes the city of Cambridge, which is naturally convenient. I grabbed the main osm file.

It's in XML format, which is a little unfortunate. I then used osmfilter to reduce the data to more manageable proportions.

First, I want the locations of all the bus stops. Just the nodes, no relations or ways or dependencies. The bus stops have highway=bus_stop so the following filter command should do it:

./osmfilter Cambridge.osm --keep="highway=bus_stop" --drop-ways --drop-relations --ignore-dependencies

Getting the list of places (where place is somewhere a user may use as a starting point or destination) was a bit trickier. In the end I made the assumption that everywhere of interest would have a postcode. It's not quite true, but I'm just interested in the distribution here so it will do as a first approximation. That gives me a filter command like:

./osmfilter Cambridge.osm --keep="addr:postcode=" --drop-ways --drop-relations --ignore-dependencies

The format of the XML is quite simple, it splits things up nicely onto separate lines. This makes it very easy to use basic Unix tools like grep and awk to pick out the lines that have latitude and longitude on them which gives me lists of coordinates.

I then put together a very cheap and cheerful Java program to read the files of coordinates and calculate the distances between all of them, using a simple equirectangular approximation as described here. The first run of ~10000 places and ~1000 bus stops took less than half a second to print the distance to the nearest bus stop, so I wasn't going to optimize it any further.

The most immediate question can then be answered - what is the distribution of distances to the nearest bus stop? A quick hack using the dist prefab in ploticus and I get the following graph:

That's number of places against distance in meters, 10m bins.

This is really quite interesting. It shows that most places in Cambridge are within a few hundred metres of a bus stop. In fact, almost all are within my acceptable distance.

In reality, it's not quite as good as that. The first thing to correct for is that these are distances as the crow flies. Actual walking distance would be a little further - it's probably reasonable to multiply by 1.4-1.5 to allow for corners, curves, and crossings. Even then the bulk of Cambridge is still inside that 300m range.

The other problem, and it's a much bigger problem, is that this measures the distance to a bus stop, not to a bus service. A significant number of the bus stops in the data are no longer in use. Short of hand-editing those out I'm not sure how to approach this.

Furthermore, of those bus stops that are in service, you have to make allowances for the timetable. If there's only one bus an hour (some bus stops are one or two a day) then you have to make some allowance for that. One simple approach would be to calculate the time to next bus, which would be the walking time plus half the time between buses. (I'm prepared to use the peak frequency here. In reality people would time their setting out to align with the timetable rather than it being random, although the less frequent a service the earlier you aim to arrive to make sure you don't miss a bus. It's complicated.)

It would be nice to show the distances on a map, which would give you a much better visualization of where in Cambridge has good or bad access to a bus service. But that's only really worth doing if you have better data.

At the present time only a couple of dozen bus stops in the OSM dataset are annotated with the necessary information to allow more detailed analysis. It would be nice to get more accurate metadata (and to have the stops in the right places). There's a local Meetup group, but it's not terribly active. Still, the whole point of OpenStreetMap is that it's freely editable by anyone.