Kumamoto's Car Society Cannot Be Solved by Roads — Transit's Downward Spiral and Planning Backward from Where People Live

Congestion is worsening in the Kumamoto urban area, where semiconductor industry is concentrating. The account carried by FIRST-HAND Local also describes a life leaning ever harder on the car.

The car's share rose eight points in 26 years

The Kumamoto Urban Area Person Trip Survey, compiled by Kumamoto Prefecture and Kumamoto City among others, compares three points in time on the same measure. The share of trips whose main mode is the car rose to 59.3%, 64.4%, and 67.3%[1] — eight points in 26 years. Public transit moved 5.9%, 5.9%, and 5.2%[1]. The bicycle roughly halved, from 16.3% to 9.4%[2].

What is falling is the bus

Open up the transit figure and the decline turns out not to be uniform. The bus share fell steadily, at 4.1%, 3.8%, and 2.8%[1], while the tram rose from 0.7% to 1.0%[2] and rail from 1.1% to 1.5%[2]. Transit as a whole lost 0.7 points, but that is a bus losing 1.3 points and fixed-track modes gaining 0.7. Transit was not abandoned across the board; one particular form, the route bus, is thinning out.

Total travel has in fact fallen

There is a second fact that is easy to miss. Travel in the urban area is not growing. Total trips rose from 2.274 million a day in 1997 to 2.753 million in 2012, then fell in 2023 to 2.335 million trips per day, 0.85 times the 2012 level[3]. The share of people who go out at all moved 83.2%, 88.5%, and 79.0%[1] — peaking in 2012.

Split by age, the fall is uneven. Trips by people aged 15 to 64 dropped to 0.74 times their 2012 level[4], from 1.943 million to 1.442 million. Those aged 65 and over, by contrast, rose to 1.13 times, at 625,000[4], and those aged 5 to 14 to 1.04 times, at 268,000; neither fell. Against 1997, trips by people aged 65 and over went from 224,000 to 625,000 — 2.8 times as many. The working-age population moves less, and travel by older people has piled up in its place.

That congestion does not ease as total travel falls has something to do with this substitution. What fell was travel by people aged 15 to 64, which concentrates in commuting hours; what grew was travel by older people, which spreads across the day. How a total moves and how a given hour jams need not move together.

Travel across the boundary of the urban area has fallen too. Trips that begin and end inside the urban area came to 0.88 times their 2012 level[4], while trips crossing the boundary fell to 0.60 times[4]. Travel is contracting inward.

What gets lost when a single figure is put in the headline is exactly the point set out in an introduction to statistical literacy（このサイトの記事）. Look only at mode share and car dependence has deepened; look only at the total and travel has fallen. Both sit in the same table of the same survey.

A caution belongs here. Multiplying the published mode share by the published trip total, car trips work out at roughly 1.77 million a day in 2012 against roughly 1.57 million in 2023 — lower in absolute terms. Worsening congestion, then, cannot be explained by traffic volume across the urban area. That the car's share rose and that congestion got worse are two things that each need their own explanation.

Adding roads has not reduced congestion

Measures have been taken. Road improvements aimed at easing congestion have continued in the Kumamoto urban area. Congestion has not fallen. On the ground, people say that adding roads does not reduce it. The arrival of semiconductor plants generated demand beyond what infrastructure designed on a 20-year cycle assumed — concentrated in particular places and particular hours. Even when the urban-area total falls, roads jam wherever traffic gathers.

Easier use draws more demand

That adding roads fails to reduce congestion is not peculiar to Kumamoto. Widen a road and make it easier to drive, and people who had held back start driving, so traffic itself grows. The pull runs toward more demand. In the national expressway toll-free trial, lowering only the price barrier raised traffic on the target sections from 8,600 vehicles a day before the trial to 15,400 — about 79% more[5]. Going toll-free lowers price; widening a road lowers travel time. The instruments differ, but in both cases making the car easier to use draws more demand. On that reading, widening roads risks pulling in new traffic rather than clearing congestion.

The hands to run the service are themselves short

Meanwhile the transit that ought to absorb that demand is thinning. Drivers run short, services are cut, routes are abolished. It becomes harder to use, riders fall away, the books worsen, and services are cut again. This downward spiral is turning in region after region. Bus drivers are projected to fall from 116,000 in 2021 to 93,000 in 2030, a shortfall of 36,000 against the 129,000 needed[6]. Fewer hands to run the service means transit shrinks further. That the bus alone keeps falling in Kumamoto's mode share is this national contraction showing up in local figures.

Congestion and transit blanks grow from the same root

The wider the areas where one cannot live without a car, the less transit can hold up. The national government calls areas that route buses and the like do not reach "transit blanks," and has acknowledged about 2,500 of them nationwide[7]. Congestion and transit blanks are two faces of the same root: car dependence.

Planning backward from location has begun

If so, the move is not to widen roads further. Since easier use draws more demand, widening turns into a chase. What is needed is to work backward from a form in which transit can hold up, and reconnect housing with transport. That has begun. According to MLIT, of the 527 cities that drew up a location optimization plan for compact urban development, 424 municipalities also drew up a regional public transport plan[8], beginning to think about where people live and how they move as one.

The rise in fixed-track modes in Kumamoto's figures offers one clue in this direction. Trams and rail run where their tracks run. If housing and errands gather along the line they get used; if not, they do not. Nor can they be folded up and withdrawn as easily as a bus route. Designing location and transport together is not an abstract ideal; it is already showing up in how the mode shares move.

Where the fork lies

Keep adding homes in places where one cannot live without a car, or redesign location by working backward from where transit can hold up. That is the fork. Every road added brings more cars, transit thins, and transit blanks spread. Stopping the chase calls for thinking about where people live from transport, rather than adding transport afterwards.

Congestion arises not from a shortage of roads but from a misfit between how people live and how they move. What Kumamoto's figures show is a specific misfit: travel across the urban area is falling, yet traffic gathers in particular places at particular hours and jams. Whether that misfit can be reassembled head-on is what decides whether a region can keep its people moving.

Further Reading

• 地域再生の戦略 「交通まちづくり」というアプローチ (A Strategy for Regional Renewal: The "Transport-Led Town Building" Approach)（外部サイト、新しいタブで開きます） (Kiyohito Utsunomiya, Chikuma Shinsho, 2015) — rethinks car-dependent society and sets out transport-led town building around public transit, drawing on cases at home and abroad. (In Japanese.)

References

Kumamoto Urban Area Person Trip Survey: Summary of Results — Kumamoto Prefecture. Kumamoto Prefecture

On Conducting the Kumamoto Urban Area Person Trip Survey (FY2023) — Kumamoto City. Kumamoto City

On the Status of the Expressway Toll-Free Social Experiment — Ministry of Land, Infrastructure, Transport and Tourism. MLIT

Current State and Challenges of the Bus Industry (material submitted to an MLIT council) — Japan Bus Association. MLIT Transport Policy Council

Bill to Partially Amend the Act on Revitalization and Rehabilitation of Local Public Transportation (resolving transit blanks) — Ministry of Land, Infrastructure, Transport and Tourism. MLIT

Coordination between Location Optimization Plans and Regional Public Transport Plans — Ministry of Land, Infrastructure, Transport and Tourism. MLIT