03What role does transport play in densifying city centres?

While much is said about transport and the need for investment in it, there is little information about the performance of transport systems across cities. This, coupled with current and likely future demand generated from the growth of city-centre economies, is an important assessment to make when deciding on investment in new transport infrastructure. To what extent is the lack of transport a barrier to city centre success? And do all cities need additional investment in new transport infrastructure?

This section looks at data from the NIC that aims to provide a sense of how quickly the transport system in a city links people to job opportunities in city centres (see Box 6). This includes travel by private car and public transport, and combines it with data on how people use the existing transport system to access city-centre jobs to understand where transport may be holding back growth.

The NIC data is not perfect. It is limited in that it looks at the average journey and so does not allow for bottlenecks – the average journey for a city may be much quicker than some commuters experience on specific routes. In addition, as Box 7 makes clear, the built-up areas used in the data do not always align with the primary urban areas, which Centre for Cities considers to be a better reflection

of the functional economic geography of the places. Nevertheless, the data provides important insight and a consistent national comparison for the nature of transport provision and use in these cities and large towns and how it relates to economic performance.

Congestion is not a major issue into many city centres

In most places accessing city-centre employment by the fastest route is reasonably quick, even at peak times. Figure 3 uses the NIC data to set out the performance of transport networks in British cities and large towns in order of the fastest possible journey into the city centre. The light green bars show the accessibility for a journey by the fastest mode – which the NIC’s modelling calculates is always by car – whereas the purple bars refer to the speed of the journey by the quickest public transport route.

The most striking finding from the data is that, in most places, congestion is likely to be a minor constraint to linking workers with city-centre jobs even if there are some bottlenecks and delays on a few roads at the height of rush hour. Figure 3 shows that in 45 of the 57 cities and large towns measured, the city-centre jobs accessibility score (the fastest journey) is between 0.70 and 0.79 where a score of 1 would indicate a “perfect accessibility”.⁹

Those with the best NIC accessibility scores are either:

• Strongly-performing cities or new towns with relatively small city-centre economies, such as Aldershot, Telford and Crawley. In these places, the more dispersed nature of jobs means that there are fewer bottlenecks which hinder a smooth commute to For new towns such as Milton Keynes, which were planned and built for travel by car, their high-capacity road networks have been able to handle the levels of demand to travel into the city centres even where this has grown rapidly.
• Places with weaker city-centre economies, such as Derby and Doncaster, have good intra-urban employment accessibility as the low number of jobs in the centre means there is lower demand to travel there. As a result, the existing capacity of the road network supports largely free- flowing traffic on average. In these cities, good car accessibility is a symptom of a weak city centre

City-centre accessibility decreases with increasing jobs density

According to the NIC data, those cities with the lowest accessibility scores are those with the densest city centres, i.e. those city centres that have the largest funnelling of commuters into them at peak times, and show consequently higher levels of congestion. Figure 4 illustrates this negative relationship between the NIC accessibility score (irrespective of mode) and the density of jobs in the city centre. In the bottom-right quadrant – B – are city centres such as Manchester’s, which has 268 jobs per hectare and an accessibility score of 0.63, and London, which has 543 jobs per hectare in the city centre and an accessibility score of just 0.45.

In contrast, city centres in the top-left quadrant – D – are much less dense and have much faster access according to the NIC data. This includes centres such as Aldershot, Telford and Newport. Aldershot’s centre for instance has just 38 jobs per hectare and a higher NIC accessibility score of 0.81. Congestion into these city centres is much less of an issue on average.

It is the economic geography of a city or large town that plays a fundamental role in the speed of the transport system into the centre. An increasing number of jobs in the centre, which leads to an increase in journeys into it, necessarily slows down commuting by private transport as more cars compete for limited road space.

These patterns tend to influence whether a commuter decides to travel by public or private transport. As the bubbles in Figure 4 show, commuting by public transport increases as density increases and accessibility falls. While only 12 per cent of city-centre workers in Telford (the place with the highest accessibility score) commuted by public transport in 2011 (the most recent data available), 80 per cent of London city-centre workers did so.

This occurs because of the shift in balance of the relative costs and benefits between travelling by car and public transport that a larger city-centre economy creates. As the NIC data above shows, car travel is still quicker than public transport into every city centre in Britain. But the narrowing of this gap for the densest city centres, combined with other associated costs, such as parking charges, and in London’s case, the Congestion Charge, means that in Manchester and Birmingham around half of all city-centre commuters chose public transport in 2011.

Of course, public transport is not the only alternative to the car – walking and cycling are options too. But these options are far more popular choices in smaller cities such as Cambridge and York (where walking and cycling account for 41 per cent and 40 per cent of city centre commutes respectively) than for larger cities such as Liverpool or Manchester.

Bristol stands out as a major city with very high levels of walking and cycling into the city centre (32 per cent), which is a function of the higher share of city centre workers living in neighbourhoods around the city centre. These may be desirable because of the quality of housing, schools or shopping and cultural amenities. It may also be that the weakness of public transport accessibility further out from the city centre puts a higher premium for city-centre workers on housing within walkable distance.

There are two implications. Firstly, a growing city centre needs a transport system that allows an increase in commuters into it, and significant growth requires substantial public transport capacity as the roads become congested for cars.

Secondly, most cities with weak city-centre economies — those in quadrant D — have significant road capacity to support jobs growth in the city centre without leading to congestion. These weaker cities should focus on encouraging more jobs to locate in the city centre and maintaining bus speeds. It is unlikely that new public transport infrastructure or upgrades will be of tangible economic benefit to residents or businesses in these cities in the short- or medium-term.

In contrast to the strongly-negative relationship between city-centre accessibility by car and jobs density, the relationship between public transport accessibility and jobs density is bell-shaped: accessibility to the city centre initially increases with jobs density but decreases after having exceeded a certain level of density (see Figure 5).

It is particularly the weaker and less-dense city centres that have worse public- transport accessibility. Lower demand to access the smaller number of jobs in the weakest city centres makes public transport less viable, meaning less frequent services that increase average waiting times and worsen public transport accessibility. Conversely, denser and stronger city centres generate higher levels of demand for services to access more jobs. This supports the provision of more- frequent city-centre services to meet this demand, bringing down average waiting times for passengers and increasing public transport accessibility.¹⁰

Figure 5 suggests that there is a turning point in this relationship. While the relationship is positive up to around 200 jobs per hectare, after this point public transport accessibility begins to fall. This could be because greater competition for road space slows buses down after a certain point, or the necessary increase in traffic lights and junctions makes journeys longer. As the bubble sizes suggest though, this does not appear to deter public transport usage, suggesting that public transport remains the most efficient mode of transport to get people to work in these cities.

In part, this is because of other public transport options that are available that are not competing for limited road space. In these cities, the rail network has overtaken the bus or car as the single most important transport mode to access the city centre at peak times. Rail journey reliability and times are less affected by the higher demand that worsens car and bus accessibility. This does mean though that residents reliant on buses have seen their feasible commutable distance shrink (see Box 9) while rail commuters have seen the number of jobs they can access grow.

Besides London, seven cities — Manchester, Birmingham, Bristol, Leeds, Edinburgh, Glasgow and Cardiff — have city centres with jobs density above 200 and public transport accessibility of 0.3 or below. Manchester, Leeds and Birmingham in particular stand out for their slow public transport.

The more reliable and faster parts of the public transport networks into the city centre at peak times, such as rail, tram and busways, are at capacity, while buses exposed to road congestion have spare capacity largely due to unreliability and unjustifiable commuting times (see Figure 6). The future jobs growth in these city centres is most at risk of being constrained by their inadequate transport infrastructure.

A lack of spare capacity supports the case for further major infrastructure investment

As well as speed, capacity is also an issue that should be considered when looking at the performance of the transport network and requirements for investment. A system with a lot of spare capacity is unlikely to need large infrastructure investment. While data on usage is patchy, estimates are available for the primary centres of England’s combined authorities (see Figure 6).¹⁴

This more limited dataset suggests that the denser the city centre, the less spare road and train capacity there is. In the West Midlands, for instance, 83 per cent of road capacity, and 63 per cent of national rail capacity in the city centre is being used at peak time – one of the highest of any of the areas measured.

But the averages presented in this overall city score do not capture particular lines and routes into city centres that are at capacity. In Greater Manchester, for instance, the Metrolink line from Altrincham into Manchester city centre is full at peak times and has been since soon after opening, leaving some commuters unable to board services, while elsewhere on the network, peak-time trams from Rochdale are not full.¹⁵

Bus capacity stands out for its lower capacity utilisation. In several of these cities, the share of bus capacity used into the city centre is much lower than for national rail and road. In the West Midlands, less than half (46 per cent) of the bus capacity is used and in West Yorkshire only 63 per cent is used despite more than 80 per cent of road and rail capacity being taken up.

This raises the question as to why capacity utilisation is not higher given the nature of its accessibility score and the density of its city centre. Work by the Open Data Institute Leeds for the West Midlands Combined Authority shows that it is the inefficiency of the system – especially the irregularity of and delays to services at peak times – that makes the bus an unattractive option.¹¹ Given this, policy should look at what investments, such as bus lanes, can improve the efficiency of existing services.

‘Build it and they will come’ cannot be justification for major transport infrastructure investment

A counter-argument sometimes put forward is that investing in better public transport now will spur the growth of a city-centre economy, rather than the other way round. But the relatively free-flowing nature of the transport network into many city centres suggests that this is not a constraint on growth, and further investment will make little fundamental difference. ‘Build it and they will come’ is unlikely to be a successful strategy.

This also applies to the type of transport that infrastructure investment is used to support. While the political allure of a large new tram or underground system is clear, it may not be the most appropriate intervention. Cities should consider the mix of modes and their performance carefully when planning new infrastructure investments. Box 11 considers the case of investment in tram lines in Manchester and Sheffield.