The Sign as Building Material

I. The Book

Every bridge in Germany has a book. It is called the Bauwerksbuch, DIN 1076 requires it, and it contains everything: year of construction, structural design, tendons, every inspection since the day the bridge was signed off. Every six years an engineer arrives, climbs beneath the structure and rates each individual defect on three axes — structural stability, traffic safety, durability, on a scale from zero to four. A bridge with forty cracks generates forty separately assessed records, each traceable to a particular component at a particular location. Software then computes a condition grade between 1.0 and 4.0.

It is an excellent procedure. German engineering at its purest: standardised, repeatable, auditable, without a trace of euphemism. Anyone who has held an inspection report knows that nothing is glossed over here. There is no grade five and no grade six. Structures that are no longer safe to stand or to carry traffic fall outside the scale altogether and are closed during the inspection itself.

So at the end there is a number. At 3.4 the durability is gone and the structural stability is compromised. The engineer climbs down from the scaffold, enters the figure, signs.

And then the law says what is to be done.

II. The Sentence

Section 3(1) of the Federal Trunk Roads Act obliges the bodies bearing road construction responsibility to maintain the roads. Three words decide everything: according to their capacity. The maintenance duty is subject to a budget proviso from the outset. It is not a duty, but a duty as far as the money goes.

And then comes subsection 2:

"Insofar as the bodies bearing road construction responsibility are, having regard to their capacity, unable to carry out measures under subsection 1 sentence 2, they shall indicate an unsafe condition by means of traffic signs."

One has to read the sentence twice, because the first time through one assumes a misreading. The law describes the case in which the money for maintenance is missing. And for that case it does not order that money be obtained. It orders that a sign be erected.

Anyone who thinks this applies only to motorways is mistaken. Article 9(1) sentence 3 of the Bavarian Roads Act is word for word identical and applies to municipal roads. The other federal states use the same construction. It therefore covers precisely those roughly 67,000 municipal bridges that are the real subject here.

The traffic sign is thus the only building material whose procurement German road law expressly prescribes for the event of insolvency. It is vibration-free, weather-resistant, available off the shelf, and costs a fraction of a cubic metre of prestressed concrete. Above all, it is the only component the legislator himself recommends.

III. The Missing Plaintiff

One might object that duties can be enforced in court. Not this one.

The duty to maintain traffic safety has sharp teeth. Anyone injured on a decaying bridge has a claim in state liability, and the official responsible faces criminal exposure as well. That duty, however, can be discharged completely and at zero cost: by signage, by weight restriction, by closure. A closed bridge is a perfectly safe bridge.

The maintenance duty, by contrast, is objective law without a subjective counterpart. Nobody holds a right to have a bridge kept in repair. It appears in every piece of legal guidance on the subject, stated with dry matter-of-factness: the subjective right required for a court action is absent. There is no plaintiff. There is nobody whose rights are violated when a structure that belongs to everyone falls apart.

In Germany one can challenge the colour of a façade in a heritage district, the felling of a lime tree, the height of a neighbour's garage. Against the decay of a bridge nothing can be done, because the decay violates nobody's right so long as a sign is put up beside it in good time.

One duty costs nothing and has an opponent in court. The other costs millions and has none. What follows from that is not sloppiness. It is consistency.

Which is why the reproach aimed at the building authorities misses. The official who takes note of grade 3.4 and orders a weight restriction is not failing. He is executing subsection 2 to the letter. He is doing what the law provides for this case. He also has forty-five per cent fewer colleagues than in 1991 with whom he might do otherwise.

IV. Beneath the Carriageway

One storey down, the world looks different.

Beneath the decaying bridge, in the same municipality, under the same administration, inside the same budget deficit, lies the sewer. It is governed by the municipal charges legislation. And that legislation provides: long-lived assets such as public sewers are to be depreciated over a service life of at least fifty years and refinanced through wastewater charges. Depreciation may even be based on current replacement value rather than historic acquisition cost — expressly with the aim of preserving the substance, because only in that way is the loss of value expressed at present-day price levels.

Here the chain runs through: loss of value, charge calculation, revenue, renewal. Annually, arithmetically compulsory, reviewable before an administrative court. No discretion, no budget proviso, no capacity clause. The sewer may not be allowed to decay, because its decay generates an invoice.

The sewer beneath the road has what the bridge above it does not: someone who pays a charge. And with him a payment stream coupled to the condition of the structure rather than to the mood of a budget debate.

This should not be romanticised — the sewer networks have their own backlog, and the higher administrative courts are still arguing about the correct depreciation base. The difference is not perfection against decay. The difference is that the sewer's loss of value triggers a legally prescribed payment stream, and the bridge's loss of value does not.

V. The Circuit That Existed

One might say that charges simply cannot work for a bridge. They can. The coupling existed, even in road construction.

The heavy goods vehicle toll was introduced in 2005 to establish user financing of the federal transport network. It worked. In recent years toll revenue covered more than ninety per cent of investment in federal trunk roads. It was called the closed financing circuit for roads: whoever wears the road out pays for its renewal. Exactly the principle that keeps the sewer alive.

In 2023 the federal government decided to break the circuit open. In future only around half of toll revenue would flow into federal trunk roads, the remainder into other modes of transport.

The consequence did not take decades to appear. It took months. In spring 2024 the Federation of the German Construction Industry warned that from mid-year the motorway company would run out of money for new projects — particularly in maintenance and bridge construction. Approved repairs were cancelled and postponed because the funds for investment were lacking.

This is the point at which the matter stops being funny. The one functioning mechanism in German road administration was not damaged out of ignorance. It was opened up because a closed circuit looks, to a budget committee, much like a locked cupboard: irritating, when one would like to get at the contents.

VI. The Balance Sheet

What comes of all this can be calculated, and we have calculated it.

According to the national accounts, German municipalities wrote off more than they invested in twenty of the thirty-one years between 1995 and 2025, and continuously from 2002 to 2022. Converted to present-day prices, they consumed substance worth roughly 114 billion euros over that period.

The municipal treasurers who sit on these structures put the gap at 231 billion in the KfW municipal survey. A factor of two. That is not a contradiction but a measurement: it shows by how much straight-line depreciation understates actual decay. A structure holds for a long time and then fails quickly.

And because the country waited thirty years, the same work has become more expensive. The municipal backlog grew by 67 per cent in nominal terms since 2018, by seven per cent in real terms. That implies a pure price effect of 56 per cent. The official construction price index gives 54.8 for the same span. Two measurements from entirely separate sources, two percentage points apart.

Whoever did not repair in 2018 pays half again as much for the same bridge today. Deferral was not a saving. It was a liability bearing more than six per cent interest — well above what the federal government pays on its bonds. The country borrowed from the most expensive creditor available, namely the structure itself, and called it thrift.

And across the whole span: Germany fell below the euro area investment average in every single one of those thirty-one years. France has invested nearly twice as much for three decades. That is not a business cycle. It is a constant.

VII. Everything Has Been Said

One might assume this is new. It is the opposite of new.

In December 2012 the commission on the future of transport infrastructure financing delivered its report, chaired by Karl-Heinz Daehre, a former state transport minister of the Christian Democrats. The finding: across road, rail and waterway, the federal government, the states and the municipalities are short 7.2 billion euros every year. A year later the commission on sustainable transport infrastructure financing under Kurt Bodewig, a former federal transport minister of the Social Democrats, confirmed those findings and set out a timetable for implementation. Both commissions proposed earmarked, stabilised financing channels — funds placed beyond the reach of annual budgets.

Two former transport ministers, two parties, the same diagnosis, the same therapy. The institutional proposals were not pursued. No corresponding increase in funding was set in motion, which is why the backlog has grown ever since.

What is missing is therefore not insight. Not data, not standards, not commissions, not reports. The state does not suffer from blindness. It sees excellently, at standardised resolution, assessed on three axes, refreshed every six years.

What is missing is a sentence.

VIII. The Missing Second Sentence

It would have to read roughly as follows:

"The bodies bearing road construction responsibility shall enter in their budgets, and cover, the annual loss of value of their engineering structures as determined according to the recognised rules of engineering. Sentence 1 is not subject to the proviso of capacity."

The second of those two sentences runs to nine words in the German original. It is the entire difference between the sewer and the bridge above it. For the sewer it has stood in the law for decades, in the language of charges. For the bridge it stands nowhere.

It will be objected that such a sentence is unaffordable. It is not, because the bill is running in any case. It simply runs invisibly, without a budget line, without a decision, without anyone responsible — and at a rate of interest no treasurer would accept if somebody were obliged to state it as a rate of interest.

It will be objected that this could never be enacted. That is probably true. A structure has no vote, no mandate and no standing to sue. All it can do is collapse, and even that it usually does at night.

Until then, subsection 2 applies. Until then the sign remains the most dependable building material in the republic: quickly procured, immediately effective, legally impeccable. It does not hold up the structure. But it does hold up the authority.