Transport planning and DRT

The Padam Moblity transport planning team works on how to use DRT to help ensure that more people have better access to public transport. Here's how...

DRT bookings enable us to see the desire lines for transport – the most popular origins and destinations for journeys

DRT bookings enable us to see the desire lines for transport – the most popular origins and destinations for journeys

Some areas of the UK have become transport deserts, served by public transport a few times per week if at all. This worrying trend has come into focus as the need to cut transport emissions has become more pressing.

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With the tool of DRT in our transport planning toolbox, we can design a network to meet more people’s needs, more of the time – and start to make transport deserts bloom

At the same time, social and economic issues (for instance the productivity gap between the UK and its European neighbours) point to the absence of public transport as a factor in deprivation and economic lassitude.

Reversing the desertification trend is a tricky long term project, but it’s one that progressive local authorities are tackling.

The Padam Moblity transport planning team works on how to use DRT to help ensure that more people have better access to public transport.

We use our transport planning tools analyse the existing transport network and the population and work out the best way to link them together.

From this analysis we can simulate usage to show authorities the journeys we would anticipate, and look at different scenarios and configurations.

This is an inexpensive way to help authorities make decisions about their network and where DRT can improve it. Once we have demonstrated different options we use them to suggest DRT pilots and their impacts.

Transport connections and fixed routes

Transport connections and fixed routes can be a difficult match, particularly in rural areas. To illustrate the kinds of situations we tackle, imagine you're trying to get passengers to a railway station where trains leave every 30 minutes in each direction - so, every hour there's a train to Town A or Town B.

This frequency of service isn't unusual for a smaller rural station - indeed you could argue it's pretty good these days - but it creates headaches for anyone planning a feeder service using a fixed route bus.

Bus speeds on rural roads aren't stellar. On smaller roads, or passing through settlements, they may be around 20 mph average speed moving (not including stops). Even if the overall average speed is 20 mph, this means the longest possible route you can cover with a single vehicle while still offering an hourly connecting service is 10 miles (because the bus will need to make a return journey too).

Once you factor in the distance users are willing to walk to stops (which can be very low for elderly passengers, or anyone with small children in tow) the population covered by a service shrinks still further.

Then there is the question of when to drop off and pick up your passengers at the station. The wait for a connection affects not just the journey time but also its overall quality, especially if it's at a small station with no facilities.

Ideally there needs to be enough time between the bus arriving and the train departing that a couple of minutes' lateness won't cause a missed connection, but also not so much that passengers are left waiting on a cold, exposed station platform for a protracted period of time.

If the bus visits the station every hour, it might be the case that it can only connect well with services to Town A, while the train to Town B may involve a wait of 20 or 30 minutes. 

What about passengers arriving to catch the connecting service? You could factor in some layover time at the station but that would reduce the overall length of route than you can serve while still keeping the same frequency. 

Advantages of DRT

Under these circumstances the DRT model of putting in a booking via a call centre or an app, being collected from outside or near your front door, and being able to divert or change should something happen to the connecting train, starts to look very appealing.

A second advantage for DRT is that the buses can take a more direct route. If a fixed bus route is programmed to travel near more homes (enabling it to pick up more people) this generally means diverting the route so that it’s not direct.

For instance, it may pass through a housing estate off the main journey trajectory or, in rural areas, via a village, creating a less direct and much longer route with more stops.

Obviously there is no guarantee that there will be people at all those stops, however the bus is still obliged to follow the time table. This extends the lengths of journeys making them longer than the equivalent trip by car, often by several times the journey time.

In contrast, DRT only diverts to pick up known passengers, and whilst the trip will be longer than the trip by car, the difference is much smaller.

All these considerations go into designing the provision of DRT. But it doesn’t stop there. Once there is a pilot in place our transport planning team can simulate different scenarios to work out how to improve performance. Are more vehicles required at certain times of day or could some be cut and journeys reorganised to ensure the same performance? 

The longer term impact is that the network is being designed with knowledge of where people want to go. DRT bookings enable us to see the desire lines for transport – the most popular origins and destinations for journeys.

Origins and destinations, together with the times of day people are requesting trips, create indicators we look for to see whether the routes can be adapted to semi-fixed or fixed at certain times of day.

As ridership increases, this becomes more likely and more practical. Using desired trips on DRT as a guide also means that any fixed lines can be optimised for the journeys people want to make.

Of course, the limitations of fixed lines won’t meet everyone’s needs, so it’s unlikely to completely remove the need for DRT, however, creating a mixed of fixed and DRT services can optimise the overall network.

With the tool of DRT in our transport planning toolbox, we can design a network to meet more people’s needs, more of the time – and start to make transport deserts bloom.