Efficient for whom, and by what measure?
People use “efficient” to mean different things. For a driver, an efficient city might mean fast, uncongested roads. For a city treasurer, it might mean low cost per trip. For an environmental planner, low emissions per passenger. For a person without a car, it might mean being able to reach work without spending hours on the way. Each view is legitimate, so a meaningful discussion of efficient urban transport begins by choosing which measures matter.
This article uses a broad definition: a city moves people efficiently when it takes them where they need to go, with reasonable travel time and cost and dependable arrival, using relatively little space, money and pollution.
Four useful measures
Capacity per unit of street space. How many people can a street move in an hour? This depends on the mode and how full vehicles are. Walking and cycling carry many people in narrow strips. Buses and trams can carry a lot if frequent and well used. Private cars carry the fewest people per unit of road width, mainly because each car usually carries only one or two occupants.
A simple, hypothetical comparison illustrates the idea. Suppose a bus carries 40 riders, and the average car carries 1.5 people. Then 40 riders in cars would need about 27 cars (40 divided by 1.5 is roughly 26.7). Each car is also longer than a person and needs room to stop and maneuver, so those 27 cars take up much more street length than one bus. These numbers are examples, not measurements; real occupancy varies greatly, and a nearly empty bus is far less efficient.
Travel time. What matters is the door-to-door trip, including walking to a stop, waiting, riding, transferring and walking to the destination. A mode that is fast on the move but hard to reach may be slower overall than a slower mode that starts at the door.
Cost. Includes cost to the traveler (fares, fuel, parking, vehicle ownership) and cost to the public (building and maintaining roads and transit, subsidies and the cost of crashes and pollution). The two are often different. Driving can look cheap to an individual because roads and parking are subsidized, while the full cost to society is larger.
Reliability. People value knowing how long a trip will take. A route that averages 30 minutes but sometimes takes an hour forces travelers to leave extra time. Reliability often matters as much as average speed, especially for work and appointments.
How the modes compare
- Walking is efficient for short trips, with no operating cost and minimal space needs. It is limited by distance and ability.
- Cycling offers good speed for medium distances at low cost, within terrain and weather limits.
- Transit is efficient on busy corridors where vehicles are well filled, and inefficient on thin routes with few riders. Dedicated lanes improve its reliability.
- Cars offer door-to-door flexibility and are efficient for trips in sparse areas, trips with loads or companions, and times when transit is unavailable. In dense areas they are space-hungry, and congestion lowers their reliability.
- Freight and delivery are also part of the system, and urban freight takes up street space and curb space that people-movers also need.
The general lesson is that no mode is efficient everywhere. Efficiency comes from matching modes to conditions, and from making the less space-intensive modes attractive where space is scarce.
What shapes efficiency
Land use. If destinations are close, trips are shorter and options greater. Density and mixed uses make high-capacity modes viable. Studies of density and public costs suggest that providing services to compact areas can cost less per household in some respects, though findings differ and congestion or land costs can offset savings.
Street design. How space is allocated affects who can move easily. Priority lanes, wide sidewalks and well-timed signals change the efficiency of each mode.
Parking policy. Plentiful, cheap parking encourages driving and spreads destinations apart. Parking minimums are among the rules that shape the costs of development and choices of travelers.
Pricing. Charging for road use or parking can make better use of limited space, though it raises fairness questions and needs public acceptance.
Operations. Signal timing, schedules, incident response and maintenance all influence reliability.
Efficiency is not the only goal
Aiming for efficiency alone can lead to poor outcomes. A system that moves the most people quickly might ignore safety, equity or quality of life. Wide, fast roads may seem efficient for vehicles but divide neighborhoods and make walking unpleasant. A fair system also considers people with limited mobility, residents who rely on irregular schedules, and those who live far from high-quality service.
There are also trade-offs between efficiency measures. Fewer stops make transit faster but increase walking distances. Lower fares may increase ridership but reduce revenue. Reallocating street space improves capacity for some modes and reduces it for others.
Using measures wisely
Cities that track a range of indicators, including person throughput on key streets, average door-to-door travel times, transit on-time performance, cost per trip and the share of jobs reachable within a given time, get a fuller picture than speed counts alone. Reading them carefully is important, because measures can be manipulated or can hide problems for particular groups. Results should be compared over time and with comparable places, and uncertainty acknowledged.
Efficient cities are built from many small improvements to land use, street design and operations. No single project makes a city efficient, and efficiency gains in one area may be offset elsewhere, so ongoing measurement and adjustment are part of the work.