posts in ‘transport’

solving the traffic problems of Cambridge, UK

Many of these ideas are now being developed by the Smarter Cambridge Transport group, led by the author of this post.

options to reject

bus lanes/ways

the Cambridgeshire Local Transport Plan and first phase of the City Deal transport initiatives contain some excellent, eminently worthwhile schemes, but the main solution that councils are proposing for solving Cambridge’s congestion woes is to build bus priority lanes or busways. the hope, based more on intuition than evidence, is that this will persuade more people to leave their cars at home and take the bus, or use park-and-ride. however:

  • the cost is huge (£60m estimated for Madingley and Milton Roads);
  • new bus lanes increase road capacity as far as the city outskirts; since we cannot increase vehicle capacity of central Cambridge streets, the additional traffic (even if only buses) will exacerbate congestion in the centre;
  • in most cases there is only space to provide a single bus lane, so buses only benefit during one (typically morning) peak period; (tidal lane allocation is theoretically possible, but not practical or safe on space-constrained urban roads with junctions, e.g. because bus stops have to be built on both sides of the lane, and the lane has to be physically segregated to prevent other vehicles straying into the path of a bus approaching from an unexpected direction);
  • every arterial (and orbital) road is heavily congested, so increasing capacity on just those that have space for a bus lane will not solve the problem city-wide;
  • much green space would be lost in widening roads;
  • the space required for a single bus lane could provide two, high quality, 2.5m cycle lanes at lower cost, which would benefit more people at all times of day;
  • there would be no improvement to air and noise pollution, even if the buses run on electricity or hydrogen (because there will still be the same volume of cars, vans and lorries on the roads).

congestion charging

congestion charging is attractive to councils because it would create a new source of revenue; and it would work: the charge just needs to be set high enough. but it has two unpalatable side effects:

  • entering the city becomes a rich man/woman’s privilege;
  • businesses that require vans (for deliveries, or providing building, installation, maintenance or repair services) become subject to a significant new tax, inhibiting growth and competition. would a plumber drive into the city to quote for a small job if s/he has to pay a congestion charge?
  • administration and enforcement is costly, requiring a high charge simply to break even.


a logical solution to congestion above ground is to create additional capacity for transport underground. however, tunneling is hugely expensive, at around £30m per kilometre, added to which is the cost and disruption of building underground stations in a city centre. this level of investment can be justified for a large city where daily ridership is in the high tens of thousands (the Tyne and Wear Metro carries around 100,000 people a day); but in a city the size of Cambridge, the investment cost per passenger-journey would be unjustifiably large.

a new vision for Cambridge

we need a shift in mindset about cars entering city centres: that they are for people with impaired mobility and for transporting goods and equipment. except where it is impractical (and not just less convenient), workers, school children, shoppers and visitors should be walking, cycling, or using public transport to access the city centre. and it’s not only because of congestion that we should be reducing the volume of traffic and parking in city streets: it’s to make them enjoyable and safe spaces for residents and visitors.

this can be achieved – and permanently – by implementing the following measures:

  • use ‘gating’ to shift congestion to outside the city: this means buses and other traffic flows freely within the city, and drivers approaching the city can make an informed decision about using park-and-ride rather than ‘chancing it’.
  • build more park-and-ride sites to minimise the distance people must drive to reach one.
  • provide more bus services.
  • reduce car parking provision in the city centre, releasing space for cycle parking, planting and other uses.
  • create convenient, continuous, connected and safe foot- and cyclepaths wherever possible in the city and out to all surrounding villages.
  • use IT to make public transport more user friendly.
  • support the creation of a city wide shopping delivery service.

the proposals here are very much work in progress: all comments and suggestions welcome!

build new city ‘gates’

the first step in curing Cambridge’s congestion problems permanently is to ‘gate’ all of the arterial roads into the city. the technique is a form of integrated traffic management and is used to good effect in Zurich. it is also known as ‘queue relocation’: congestion in the city centre is shifted to out-of-city sites where it is easier to build additional road capacity.

at each gate, the road is widened to create holding lanes for traffic wanting to enter the city; traffic lights, connected to queue detectors in the road ahead, release vehicles only as fast as they can move along the road ahead. a bypass lane permits certain classes of vehicles, such as emergency services and buses, to jump the queue. other classes of vehicle might also be permitted to use it, such as taxis, delivery vehicles, tradesmen, and multi-occupancy vehicles (to incentivise ride sharing).

building a park-and-ride site close to a gate means drivers can make an informed decision about whether to proceed into the city or use park-and-ride. road-side notices can inform drivers of expected queuing times and give directions to the nearest park-and-ride site.

this is a list of all the gates that would need to be built, starting from the south and working clockwise around the city:

Girton park and ride site

new park-and-ride site at Girton

  • A1309 (Hauxton Rd): the gate would be on the city side of the main exit from the existing park-and-ride site. Vehicles would not be permitted to enter the city from the park-and-ride site so as to prevent people driving through the site to skip the queue. The bypass lane would also serve to access Addenbrooke’s Rd.
  • A603 (Barton Rd): the gate would be about 500m beyond the roundabout and there is space to build a park-and-ride site either side of the road.
  • A1303 (Madingley Rd): this requires two gates, one about 500m beyond the A428 roundabout, with a park-and-ride site being built near the roundabout; the second gate would be just beyond the entrance to the existing park-and-ride site (which would be restricted to park-and-cycle/walk – see below).
  • A1307 (Huntingdon Rd): the gate would be where the existing dual carriageway ends and a park-and-ride site can be built in the triangle of land within the M11-A428-A14 interchange. the northbound carriageways would become a two-way road as far as the park-and-ride entrance.
  • Oakington Rd: the gate would be south of the junction with New Rd, which would provide access to a new park-and-ride site on the Guided Busway on the north-west edge of Histon.
  • B1049 (Histon Rd): the gate would be just north of the junction with Kings Hedges Rd, with the possibility of a small park-and-ride site to the west.
  • A1309 (Milton Rd): the gate would be north side of the Cowley Rd junction. there is already a park-and-ride site north of the A14, so signs on the roundabout would need to inform drivers of the expected queuing time at the gate.
  • B1047 (Horningsea Rd): the gate would be south of the A14, and there is space for a new park-and-ride site either side of the road.
  • A1303 (Newmarket Rd): the gate would be south-west of the A14 junction, and there is space for a new park-and-ride site either side of the road. there might be a need for a second gate near the entrance to the existing park-and-ride site (which would be restricted to park-and-cycle/walk – see below).
  • Balsham Rd: the gate would be at the edge of Fulbourn with a park-and-ride site nearby.
  • Station Rd (Fulbourn): the gate would be south of the railway. there will be the option to park-and-train from here when the planned new Fulbourn station opens (date to be determined).
  • Babraham Rd: the gate would be at the junction with Haverhill Rd, with a new park-and-ride site to the north (which would also serve Wandlebury Country Park and Magog Wood). the existing park-and ride site would serve only people wanting to park-and-cycle/walk – see below.
  • A1301 (Cambridge Rd): the gate would be between Stapleford and the old Cambridge Rd through Sawston. there is space for a new park-and-ride site either side of the road.


a generous budget for doing this would be:

  • £65m for road widening at the gates (13 @ £5m average)
  • £150m for new park-and-ride sites (10 @ £15m average)
  • £10m for installing queue detectors around the city
  • £5m for the control systems

total: £230m. this is less than a third of the £853m currently allocated from the City Deal funding for transport.

reduce city car parking

multi-storey car parks

Total: 3,040 parking spaces

*excluding motorcycle bays

park-and-ride sites

  • Babraham Rd: 1,458
  • Madingley Rd: 930
  • Milton: 792
  • Newmarket Rd: 873
  • Trumpington: 1,340

Total: 5,393 parking spaces

the elephants in the room when discussing congestion are the huge city centre car parks, which together have a capacity of over 3,000 spaces: they are magnets for traffic that competes with buses. reducing parking capacity, at council car parks, on street, and on business premises has to be the next step in eliminating congestion and making roads safer and more pleasant for pedestrians and cyclists.

reducing parking capacity in the city centre entails the City Council forfeiting income (the five multi-storey car parks alone yield an income of almost £9m for the council, covering 8% of annual expenditure), so that money will have to be found in other ways.

  • charge tiered prices for multiple resident parking permits, starting at, say, £70 / £120 / £200 / £300. give a year’s notice, during which time necessary exceptions can be identified. increase the differentials by £10 each year. notify ZipCar and competitors of the intention, so that they can prepare to cater for the upturn in demand.
  • expand the residents’ parking scheme to the whole of the city (inside the A1134 plus a few areas). this will yield additional income, some of which must go to the City Council to replace income lost from reducing public car parking provision. the principal aim of the expansion would be to stop commuter parking, so the hours of restricted parking can be short (e.g. just one or two hours in a day), reducing the number of wardens needed to patrol the streets.
  • gradually reduce the parking capacity at all central Cambridge car parks.
  • convert part of the ground level (‘-1’) deck of the Grand Arcade car park into additional cycle parking (see below); convert the roof deck to a landscaped roof garden with a concession for a cafe/bar.
  • build a new eastern entrance to the main rail station from Clifton Road. link this with a footpath alongside the railway sidings to the Cambridge Leisure site and multi-storey car park (which is nearly empty during the day). have the rail franchisee (currently Abellio) negotiate with Cambridge Leisure to provide the same parking rates for rail travellers as at the NCP station car park. these measures together would relieve congestion on Hills and Station Roads.
  • gradually remove pay-and-display bays on city roads to create space for cycle parking, loading bays, and (in time) household refuse collection points.
  • double-yellow Regent Terrace and relocate residents’ parking to the southern end, keeping this busy thoroughfare clear and safe for cyclists and pedestrians at all times of day.
  • double-yellow the whole of Station Road (removing all pay-and-display bays). this will make room for high quality cycle lanes in both directions (see above).


  • encourage retailers of bulky goods to club together to run a delivery service to all park-and-ride sites (following the example of John Lewis in delivering to Trumpington park-and-ride).
  • provide covered cycle parking at all park-and-ride sites, maintaining at least 10% more capacity than demand.
  • as new park-and-ride sites are built further out from the city centre, designate inner sites for bus-and-cycle, with covered, secure cycle parking for people arriving by bus (both regular and park-and-ride services).

parking reservation system

  • fund/sponsor/license a computerised parking reservation system for all city centre car parks. gradually increase the reserved allocation at each car park over time.
  • involve retailers in the scheme so that their customers can reserve and pay for a space, then receive a rebate on presentation of their ticket (or QR code) in the shop.

cycle parking

  • new Grand Arcade cycle park

    this section of level -1 of the Grand Arcade car park could be separated off for cycle parking.

    convert an area of the southern end of the ground level (‘-1’) deck of the Grand Arcade car park (beneath the City Hotel) into a 600+ space cycle park. this would be separate from the existing cycle park. the area involved is easily isolated from the flow of vehicle traffic. the only structural work required would be to widen and ramp the existing pedestrian entrances, from the City Hotel car park access lane (Tibbs Row) and from the elevated walkway alongside Corn Exchange St.

  • reassign part of each of the other multi-storey car parks to cycle parking and a cycle hire shop.
  • encourage bike hire companies to set up at park-and-ride and bus-and-cycle (see above) sites. ideally it should be possible to rent a bike one-way between any of the following: park-and-ride sites, train stations, and city centre sites (e.g. each of the multi-storey car parks).
  • aim to provide sufficient secure cycle parking within 20m of every pub and shop.
  • incentivise universities and businesses to replace all ‘wheel bender’ cycle stands with upright frames (Sheffield/Frankton/A-frame/etc.), installed at the correct height and separation (see Cambridge Cycling Campaign guide).

reduce traffic to schools

  • have the County Council employ a City Schools Transport Co-ordinator to work with all schools (state funded and private) on:
    • designating suitable car drop-off/collection points, away from congestion hotspots, in and around the city, such as park-and-ride sites, rail stations and bus stops;
    • timetabling shuttle buses between schools and designated drop-off/collection points;
    • organising adult supervision of groups of primary school children cycling or walking between school and designated  drop-off/collection points.
  • aim to introduce a ban on private vehicle drop-offs and collections in the vicinity of all schools, with exceptions being granted only by the head teacher at his/her discretion.
  • require sixth form colleges in the city to bring in a ban (with appropriate exceptions) on their students using a motor vehicle in Cambridge (extending the ban that already applies to university students – see the University of Cambridge’s Proctorial Notice on Motor Vehicles). designate a County Council officer as the contact point for the public to report vehicles that may be in breach of a student ban. the officer would pass such reports to the relevant university or school to investigate and, where appropriate, take disciplinary action.

create a Cambridgeshire transport planner

  • fund/sponsor and coordinate the development of a comprehensive Cambridgeshire transport planner for route planning and real-time travel information across Cambridgeshire, accessed via the web and mobile apps:
    • bus and train routes, timetables and real-time wait times. (consulting timetables, especially where changes of service are required en route, is complicated, tedious and outdated).
    • CycleStreets for cycle routing options.
    • carpooling organiser to enable people to request and offer rides. (this would cater to commuters and shoppers in Cambridgeshire, unlike established carpooling services (e.g. and Bla Bla Car), which focus on inter-city journeys.)
    • community transport services (e.g. Dial-a-Ride).
    • taxis (which would pay to be included).

improve city roads

  • set all bus companies operating services with intermediate stops in Cambridge a deadline of, say, 2018 by when contactless payment will be the only form of payment accepted (as it is now on London buses). this minimises stop times for buses, allowing quicker bus journey times and reduced congestion.
  • create segregated cycle lanes on all main roads with sufficient width to accommodate.
  • include a cycle-first traffic light phase at all large road junctions. the chief benefit is in allowing cyclists to turn right without crossing the path of moving vehicles. when approaching an advanced cycle box at a junction, there is often not enough time to get into the right-hand lane before the lights change and traffic starts moving.
  • paint split cycle lanes at the approach to multi-lane junctions (e.g. on A1134 approaching junction with Mill Road from the north). this gives cyclists confidence to change lane for a right-turn, and car drivers clear warning of where cyclists may pull across in front of them.
  • use sinusoidal ramps on raised tables to improve comfort and safety for cyclists.
  • pedestrian crossing

    pedestrian crossing with in-road flashing lights (instead of a Belisha beacon) © Intelligent Traffic Equipment Marketing Ltd

    install zebra crossings on all key pedestrian routes and in the vicinity of shops. a change in the highway law would enable the use of in-road flashing amber lights, which are more visible in the day than Belisha beacons and do not create an annoying distraction at night for nearby residents.

specific projects

  • remodel Station Rd–Hills Rd junction with cycle lanes on all routes.
  • remove pay-and-display bays on Station Road, enabling the addition of cycle lanes in both directions.
  • remodel junction between Downing and Corn Exchange Streets to enable cyclists to turn right safely.
  • remodel the Devonshire Rd–Carter Bridge junction to improve safety for cyclists and pedestrians.
  • Long-Road-station

    looking north: stepped access (in white) from Long Road to Guided Busway and site of new bus stop (in red)

    build a stepped link between the Guided Busway path and the south side of Long Road.

  • build a Guided Bus stop to the south of Long Road bridge. this would serve the sixth form college, Clay Farm development, Sedley Taylor Rd, Rutherford Rd, and the northern fringe of the Addenbrooke’s site.
  • build a bridge connecting Cowley Road and Fen Road; sever Fen Road at the railway; create a pedestrian and cycle underpass beneath the existing level crossing. this removes a dangerous level crossing and opens up the Fen Rd area (over 50 hectares) for future (sensitive) development.
  • create a light-controlled cycle crossing of the A1134 ring road at Natal Road to improve the link with Brookfields and the (unnamed) road that leads to Budleigh Close. this is a missing link in the east-west cycle corridor from central Cambridge to Cherry Hinton.
  • create a pedestrian crossing on Cherry Hinton Road between Rustat Road and Rock Road.
  • Brookside bridge

    new bridge and cycle path (in red) between Trumpington Road and Brookside at Fen Causeway roundabout

    build a cycle-pedestrian bridge over Hobson’s Conduit between the Trumpington Road-Fen Causeway roundabout and Brookside. This would allow cyclists to avoid the Trumpington Road-Lensfield Road roundabout, and the awkward turn and narrow bridge level with Pemberton Terrace.

  • create segregated cycle lanes along Fen Causeway, with proper junctions with cycle paths on Coe Fen, Sheep’s Green and Lammas Land.
  • cantilever a cycle path over the edge of the Mill Pond to enable cyclists to make more use of the cycle/footway to Fen Causeway on Coe Fen, and avoid the Newnham Road-Fen Causeway roundabout.

improve village transport links

putting neighbouring communities, local schools, shops and other amenities within safe walking or cycling distance reduces car use for short journeys, and has valuable social and health benefits. it also provides a free and healthy option for villagers to commute into the city, and for city dwellers to get out to the countryside and patronise village pubs, cafés and shops.

  • provide more bus services, connecting with (or serving as) park-and-ride buses for greater flexibility and speed.
  • build continuous, dedicated cycle and footpaths to connect the city with all surrounding villages (to at least the standard of the link to Great Shelford).
  • connect up village schools, shops and other amenities with safe cycle ways and all-weather footpaths.

further reading


Edward Leigh, Jim Chisholm

driverless cars

the introduction of driverless cars will be hugely disruptive, a revolution comparable to the introduction of computers, the Internet and mobile phones. it will make roads safer, taxis cheaper, and radically alter the built environment. but, just as computers made millions of pool typists redundant, so driverless cars will make millions of taxi and truck drivers redundant. it’s a case of when not if, with countries reviewing and updating legislation to legalise driverless cars on public roads.

the benefits are so attractive, especially for city dwellers, that take-up will be rapid once regulatory hurdles are cleared and driverless cars are available to the public for use on all public roads:

  • people of all ages, and physical and mental abilities will have access to personal transportation, owned, leased, shared or hired as needed.
  • roads will be much safer.
  • there will be no need for on-street parking, freeing up acres of space for other purposes.
  • fully-electric cars will be viable in cities (where most cars are parked on the street, making charging batteries difficult).
  • owning a car will not be necessary or cost-effective for low mileage travellers: driverless taxis will be cheaper than taxis now, especially for longer journeys, because fleets of driverless cars can reorganise themselves to be available where there is demand.
  • road signs may be eliminated (vehicle priorities can be arbitrated wirelessly from roadside beacons or between vehicles).


millions of truck and taxi drivers will find themselves redundant in the space of a couple of decades, a potential societal disaster. in the US alone there are 3.5 million truck drivers. to begin with, truck drivers will, for public reassurance, be employed as in-cab supervisors; drivers will be employed at depots to marshal trucks until that process is also automated; and doorstep deliveries will require drivers until they just do the delivering.

though there are fewer taxi drivers (around quarter of a million in the US), their employment prospects are bleaker as there will be a much shorter transition period than for truck drivers before they become redundant.

it is imperative that governments prepare retraining programmes at the same time as considering how to regulate and adapt infrastructure to driverless cars.


a major reservation about driverless vehicles is their safety: surely robots cannot be entrusted with human lives? the truth is that people are not as good as we like to think: on average across the world, eighteen people out of every hundred thousand die in traffic accidents each year, or about 1.26 million in 2015. the vast majority of those deaths are due to human error. here is a comparison between the weaknesses that a human driver has compared with a computerised drive system:

people computerised drive system
inattention. attention is always 100%.
misjudgement of speed or distance. a combination of GPS, cameras, radar and wireless communication with roadside beacons and nearby vehicles will provide precise information on every vehicle, pedestrian and any other obstacle’s location, velocity, acceleration, and potential collision course.
awareness only within field of view. cameras and radar will provide continuous 360° awareness.
poor night vision. infrared cameras and radar will provide almost as good awareness at night as in the day.
tiredness. computers don’t get tired.
slow reaction time (in the order of 1 second). reaction time is in the order of milliseconds.
misunderstanding of other drivers’ intentions. cars will constantly exchange data wirelessly to communicate their current state (velocity and acceleration) and planned manoeuvres.
mental overload leading to poor decisions. computers can process millions of pieces of information every second.
inappropriate response to weather conditions. systems will continually assess the road conditions and visibility and adjust the speed and manner of braking accordingly. traction control and antilock-brakes will be much more effective under computer control.
inappropriate evasive response to an imminent collision (e.g. swerving into the path of another vehicle, or braking while steering causing an uncontrolled spin). when evasive action is required, the system will already have full awareness of where it is safest to move the vehicle to.
rash behaviour owing to rage, impatience, overconfidence or showing off. computers do not feel emotions.
inadequate maintenance. a driverless car will have more self-diagnostics, and can take itself to a mechanic without inconveniencing the owner.

there will come a day, certainly by 2050, when people will wonder how we ever allowed humans, with relatively little training and assessment, to take complete charge of such lethal machines.

situational awareness

situational awareness is an important concept in the military: it involves building and continuously updating a mental map of yourself in your surrounding environment: where everyone is; what they’re doing; what they are planning to do; how they will react to any of a number of pre-examined events. it’s like a game of chess: knowing where all the pieces are on the board, the strategies at play, and the consequences of any move.

this is something that computers are particularly good at, even without possessing human intelligence. a regular desktop computer can use ‘brute force’ methodology, where thousands of scenarios are played out from the current state of the board, to beat almost any human chess player.

cars will gain situational awareness by multiple means:

  • cameras sensitive to visible and infrared light (infrared images are useful in the dark and for locating people and animals, stationary or moving);
  • radar (to locate and determine the speed and direction of other vehicles, cycles, pedestrians, animals and static obstacles);
  • sonar?
  • GPS signals (for navigation);
  • wireless communication from roadside transmitters, in particular at junctions;
  • wireless communication from nearby vehicles (say, within 200 metres), which will continuously broadcast their:
    • position
    • velocity (speed and direction)
    • acceleration/deceleration in all axes (forward-backward, left-right, up-down)
    • current and planned maneouvres (e.g. turning or changing lanes)
    • anticipated safe stopping distance

this information can be processed and mapped in real time, ensuring that all vehicles maintain a safe position on the road, at a safe distance from each other and from surrounding obstacles.

the HAL 9000 nightmare

understandably many people are reluctant to surrender control to a robot: it could malfunction in any number of nightmarish ways, killing its passengers. drive control systems will be complex, and inevitably they will contain bugs and will suffer failures. computerised visual recognition systems will make mistakes. the solution is in redundancy, using multiple systems to do similar jobs: inputs from all sensors can be cross-compared and compared with data received from nearby vehicles to create a completely accurate dynamic map of the vehicle’s surroundings. a computer system, similar to an airline’s ‘black box’, that is completely separate from the drive control system can monitor all sensory inputs and activities, checking for anomalies. where an anomaly is detected, it can initiate an emergency controlled stop and, at the same time, alert all vehicles nearby to take evasive action.


liability insurance that covers a vehicle’s driver is a legal requirement in almost all countries. in the case of an accident, each driver’s insurer pays out roughly in proportion to the degree of his/her fault. the fault might have been owing to a mechanical or electrical fault (an indicator light not working, or a brake failure), but the driver of that vehicle bears responsibility, even if s/he had taken all reasonable steps to maintain the vehicle.

for some years after their introduction, driverless cars will operate in a sophisticated cruise control mode with a manual override facility. their operation will depend on there being a responsible driver in the driving seat, ready and able to take control at a moment’s notice. the insurance model will not need to change while this is the case.

however people will learn to trust the autopilot and will cease to pay close attention to the road. drivers will still cause accidents by making mistakes when in control, or by not being attentive enough to take control when needed. so the drive systems will include increasingly sophisticated accident mitigation systems that do not rely upon, or even require, human intervention. it will then no longer make sense for the driver – if indeed there is a driver in the vehicle – to be responsible in the case of an accident.

it makes most sense for the vehicle owner to hold insurance cover for his/her vehicle, but it is not so obvious that s/he should be held responsible for any accident caused by his/her vehicle. indeed the finger would point toward the manufacturer and the software engineers behind the drive system as, it will be argued, it was their faulty or inadequate drive system that caused or failed to avoid the accident.

as long as victims in an accident are compensated by insurers in proportion to their need, it will not matter to them who or what was at fault; that will be something that the insurers will (as now) argue between themselves and with the manufacturers involved (or their insurers) where fault should be ascribed. for the manufacturers and their suppliers, the prospect of being on the receiving end of multi-million dollar law suits will provide a strong incentive to build highly robust and rigorously tested safety systems.

it will (as now) sometimes be impossible to ascribe fault, or fault may be ascribed to an uninsured vehicle owner. in these situations it is important that victims are still adequately compensated. this can be achieved either by legislating for a minimum insurance cover for all vehicle owners that covers injury for all vehicle occupants no matter where the fault lies. alternatively, countries might follow the example of New Zealand (c.f. Accident Compensation Corporation) and create a national accident compensation body, funded by taxation, that pays out entirely on the basis of need, regardless of fault.

speed limits

currently maximum legal speeds are set nationally with some local modification. for the most part it is the class of road that determines the speed limit (motorway, trunk route, urban, etc.), taking no account of local variations, such as bends, concealed junctions, road width, etc. local modifications are usually only made in response to high accident rates, and are expensive to implement.

vehicle computers will determine the optimum speed of travel algorithmically, based on:

  • what nearby vehicles are doing (which will be communicated wirelessly as well as sensed by radar);
  • curvature of bends in the road;
  • location of junctions and crossings;
  • weather conditions;
  • presence of pedestrians;
  • width of carriageway;
  • type and condition of road surface;
  • engine efficiency.

Initially it is likely that governments will want to maintain absolute speed limits, but these will become irrelevant when it is computers that continuously assess what speed is safe in context.

road signs & traffic lights

road signs can be eliminated as they serve to communicate visually to human beings information that may be communicated wirelessly.

  • directional signs will become redundant as vehicles will use digital maps and GPS receivers;
  • speed limit signs will become redundant as vehicles set their speeds algorithmically (see speed limits above);
  • traffic lights will be replaced by roadside beacons that communicate with approaching vehicles and arbitrate priorities responsively to ensure that traffic flows at optimal efficiency;
  • give-way and other junction signage will become redundant as vehicles will negotiate priorities between themselves (just as people do now at give-way junctions and roundabouts).

car sharing

car sharing schemes such as Zipcar will become hugely more attractive when cars are driverless. currently members cannot rent a car one-way: they must pay for every hour or day until they return the car to its place of origin, even if they are not driving the car for most of that time, and the car is not available to anyone else to use. a driverless car can deliver itself to another customer after each booking.

public transport

low-cost driverless taxis will compete much more keenly with public transport, especially local bus services. the risk is that city centres clog up with large numbers of vehicles carrying one or two people (and circulating empty between rides). local regulation will be essential in ensuring that this doesn’t happen. this will fall into two parts: limiting vehicle access to city centres, and promoting an integrated hierarchy of transport modes.

the only way to eliminate congestion in city centres is to limit the number of vehicles permitted access. permits should be granted on the basis of need and utility, giving priority to vehicles carrying multiple people (e.g. shared minibuses), people with impaired mobility, goods and equipment.

to ensure the most efficient use of space and the viability of public transport services, there must be seamless connections between all modes of transport: rail, bus, minibus, shared taxi, private taxi and cycle. this will ensure that shared transport and cycles predominate in city centres, and private taxis are found mainly in suburban and rural areas to provide the ‘last mile’ connection.


there will be no need for street parking: vehicles will only enter city streets to collect and set down passengers, and deliver and collect goods and equipment. only drop-off and pick-up points will be required every fifty metres or so. the released space may be repurposed for:

when not in use, vehicles will return to depots and high-density car parks, out-of-town or underground, where vehicles can be charged, serviced and valeted. the land occupied by existing city centre car parks is so valuable that it will be redeveloped for business and housing.

high capacity batteries (e.g. vanadium flow) at these car parks will smooth demand from the electricity grid. during the night, when grid demand is low, batteries of parked cars and the on-site vanadium flow battery will charge slowly. by morning, cars will be fully charged and ready to transport people to their places of work. when those cars return to the parking lot during the day, they will be charged from the vanadium flow battery (unless there is a surplus of solar or wind power available). cars will again be fully charged in time to collect people from their places of work. when those cars return, they will again be charged from the vanadium flow battery, until national demand for electricity falls to a level where everything may be charged again from the grid.

when grid supply is low, the vanadium flow batteries can feed back into the grid; and if critically low, car batteries could also be discharged to the grid. this smoothing of peak demand enables a higher proportion of power to be generated from solar and wind, and reduces the need to use gas-powered generators to meet peak demand.

refuse collection points

refuse collection will make use of driverless vehicles. in cities, where people now have to accommodate up to three bins (for compostable, recyclable, and land fill waste), it is likely that councils will gradually set up multiple collection points along streets where there were previously parking spaces. it may be that each collection point will be a car-sized refuse receptacle on wheels, possibly with a built-in compactor. the receptacle will probably have separate compartments for different categories of waste. once a compartment becomes full, the vehicle will signal for another refuse vehicle to come and replace it. if these refuse collection points were spaced about 50m apart, there would be one within 25 metres of any house. the short walk to the bins would create a new opportunity for neighbours to meet.


Edward Leigh