The rough calculation of the investment costs of the Frankfurt bridges assumes estimates at the upper end, despite the efficiency-enhancing planning intensity and effectiveness-enhancing non-profit nature of the executing management

The comprehensive and careful planning of the Frankfurt bridges as well as extensive coordination with relevant stakeholders in advance are the best guarantee for rapid implementation within the budget. The bottom-up calculated costs amounted to 29 billion, to which a buffer of around 15.5% was added, resulting in total costs of 33 billion. Of this, 20% were estimated as planning costs and 80% as construction costs. The current cost assumptions are based on the economic conditions in 2024, as a concrete project start has not yet been determined.

To estimate the costs, the upper limits of the potential cost ranges resulting from comparative figures were chosen – unlike most other infrastructure projects in Germany

Since the intensive and detailed coordination and preliminary planning of the Frankfurt bridges means that a rapid construction within the budget is to be expected, a buffer of over 15% was planned for unexpected events. Furthermore, despite the 4-5 year concept planning phase prior to the actual planning, the planning costs were set at 20% of the construction costs - the benchmark for comparable infrastructure projects shows 15%-20% planning costs

This makes sense, above all, because a very high-quality finish was assumed for all trades. When the non-profit actors in Planungsgesellschaft gGmbH and Baugesellschaft gGbmH award contracts, the focus is not on the price of a provider, but primarily on their qualifications and qualitative performance in reference projects.

Furthermore, the intensive coordination and "buy in" of all stakeholders (population, offices & authorities, politics) in advance means that the main cost driver, namely amendments, is not to be expected. Cost driver number 2, namely delays due to resistance from stakeholders (e.g. for special permits or environmental reports), is also much less likely with the Frankfurt bridges than with other projects, not only due to the detailed planning and coordination phase, but above all due to the socially and environmentally friendly design and transparent implementation by non-profit entities.

It should also be noted that the following rough cost estimate does not take inflation or other macroeconomic parameters into account. This is a simplified cost breakdown that assumes continuous framework conditions such as those in 2024, as a project start cannot yet be foreseen at that time. Appropriate adjustments will have to be made in due course. However, this does not change the fact that conceptually it is a robust, solid and viable cost structure that can serve as the basis for the feasibility of the construction project and its financing.

The buffer only includes material cost increases, wage cost increases, possible new environmental regulations and, above all, geotechnical surprises that are already foreseeable in 2024, i.e. primarily factors that cannot be avoided by planning or very good management - at least not completely. However, the highly professional management of the project planning company gGmbH and the construction company gGmbH has the advantage in return that it is not controlled by non-specialists from politics - which in turn enables professional countermeasures to be taken to counteract the cost explosion.

The Frankfurt Bridges are intended to usher in a new era of infrastructure project implementation through intensive planning and non-profit management with private investors

Planning errors and legal disputes (at least with residents, activists or authorities) can be avoided or minimized through intensive and non-profit-oriented planning. The exclusion of political influence is ensured by the legal constructions. Only completely unforeseen technical problems, especially during the foundation, could occasionally arise despite detailed geological reports.

All of these projects had the same problems that must be avoided in future infrastructure projects modeled on the Frankfurt Bridge concept:

Planning errors: Lack of coordination between the planning offices and the authorities (the consequences: errors in construction, fire protection systems not complying with the regulations, other subsequent adjustments).
Legal disputes: Disputes with construction companies and planning offices or even residents and activists
Political influence: The interference of politicians in planning and construction always leads to inefficient decisions or often wrong decisions and to additional costs.
Missing permits: Delays in permits or environmental assessments
Unforeseen technical problems: e.g. during the foundation of buildings)
Increased inflation risk as a result of these problems, leading to drastic delays in construction

Other large-scale projects serve as a model, and the concept of the Frankfurt bridges is based on their implementation parameters

What made cost compliance in these projects so exemplary is also being applied to the Frankfurt bridges:

Comprehensive & realistic planning: very detailed feasibility study and a well-founded cost estimate in advance. No overly optimistic schedules or budget estimates, but realistic calculations.

Clear financing models : with long-term repayment plans, without the need for political follow-up financing that leads to changes and delays due to political interference or disputes.

Private investors : a strong interest in cost discipline, strict tracking of budget deviations and continuous controlling (unforeseen problems can be dealt with without major additional costs).

Long-term political support based on broad, almost unbroken support among the population of all party persuasions makes it possible to avoid costly political interventions or subsequent changes or adjustments to the plan due to political sensitivities during the construction period.

Use of proven construction methods and materials in 90% of the construction, technical innovations are only used in a targeted and strategic manner in order to be tested for roll-out in other cities.

Experienced contractors: Contracts are not awarded primarily based on the cheapest offer, but rather on the basis of the greatest possible experience with similar large-scale projects in order to ensure efficient implementation.

The fact sheet of the individual areas, the data of which was collected in the feasibility study of the Altes Neuland Foundation, serves as the basis for estimating the construction and planning costs

Cost planning for the Frankfurt bridges at the upper end (1): piers and bridge body as well as excavation costs

The maximum cost for excavation is not 100 euros, but 200 euros, because excavated material during the construction of Frankfurt's bridges is not disposed of miles away as usual, but is used to create biotope hills in the immediate vicinity of the city.

For the foundation of the bridges, piers with bored pile foundations are used, with an average cost of 20,000 euros per pier.

The cost of the bridge body is estimated at 1000 euros per square meter, especially in areas of the Frankfurt bridges where there are no buildings, but only green areas (almost half of the total surface) or pedestrian or traffic routes ( approx . another 20% of the bridge surface). Even on the traffic areas, there are no heavy trucks driving on them, as is the case with normal motorway or river bridges, but only light vehicles. Depending on the section, the construction is carried out using formwork on site or (mostly) prefabricated elements at the factory.

Cost planning for the Frankfurt bridges at the upper end (2): renewal of the road surface and road signage

The construction of the Frankfurt bridges will also affect the traffic area beneath them: the area will become darker (despite numerous transparent steel lattice pillars on critical or relevant sight lines) and will need to be illuminated, and its signage will need to be completely renewed. Not only will many road signs be illuminated, but some will also be replaced by electronic display boards.

For the road surface that has to be renewed under the bridges after each construction phase has been completed, the upper limit of the comparative values of 200 euros/m2 has been chosen, as the new road surface must be both noise-reducing and comparatively light in order to improve the area under the bridges for the benefit of residents. A lighter surface for the roadways under the bridges is possible without causing as much pollution as in the areas without bridges, primarily because the vehicles drive under the bridges in the dry.

Cost planning for the Frankfurt bridges at the upper end (3): Railings and light holes of the Frankfurt bridges

Although the majority of the railings will be handcrafted, only a small proportion will actually be forged by hand. Gold plating and similar finishes are also only used sporadically, so that together with modern railings, the average cost of 5,000 euros per linear metre is at the upper end of the cost estimate.

For the light holes, the lower limit of the cost estimate of 11,000 euros per light hole can be assumed, since the Frankfurt bridges will be mass-produced for the first time and will therefore result in economies of scale not yet realized in the industry, with standard costs of probably 6,000 - 7,000 per light hole.

Cost planning for the Frankfurt bridges at the upper end (4): Three large bridges

Cost planning for the Frankfurt bridges at the upper end (5): Stairs and double elevators leading up to the Frankfurt bridges

The Frankfurt bridges have a clear finished height of 7 meters in most sections. The 800 stairs that lead up to them must be artistically designed - whether modern or traditional - especially in the inner city area, as they are in the field of vision of the residents to the right and left of the bridges, for whom every view of the world in front of their house must be spectacularly beautiful. The stairs are therefore estimated at 120,000 euros per staircase, even if the costs could be significantly lower due to economies of scale alone. The same applies to elevators and lighting: all savings that can be achieved through volume discounts from suppliers or newly realizable economies of scale in the production processes are calculated directly into the artistically sophisticated design.

Cost planning for the Frankfurt bridges at the upper end (6): Buildings

The cost of the buildings on the Frankfurt bridges is estimated at 7,000 euros per square meter. In contrast, construction costs for living space in Frankfurt in 2024 were more like 3,000 to 4,000 euros per square meter for small apartment buildings like those we find on the bridges. Of this, around 1,000 euros are for interior work and 2,000 to 3,000 euros for the part of the building visible from the outside.

The high construction costs per square meter are due to the fact that the buildings on the Frankfurt bridges are largely beautifully designed on the outside: with decorative facades, special roofs and balcony railings, etc., whereas the interior design is kept very simple (after all, these are affordable housing, women's shelters, affordable retirement homes, etc. - at least for the first 85 years of use).

However, the facade alone would not justify the high construction price per square meter, as can be seen from the construction costs for the reconstruction of old buildings :

The cost of comparatively elaborate facades for castles was between 4,000 and 5,500 euros - in 2024 this would have corresponded to 5,000 to 6,000 euros. Only a very small proportion of around 5% of the buildings on the Frankfurt bridges will be designed in such an elaborate manner (e.g. on the Art Nouveau square towards Darmstadt); around 40% will be similarly elaborate as the original reconstructions of Frankfurt's old town, another 25% will be designed like simple old buildings and around 30% will have beautiful but modern facades where the proportion of handicrafts is lower.

This results in average construction costs for the bridge buildings of 4,000 euros per square meter for the outside area and 1,000 euros per square meter for the inside area. However, to be on the safe side, the cost estimate is based on 7,000 euros per square meter instead of 5,000 euros per square meter.

Cost planning for the Frankfurt bridges at the upper end (7): disposal system

The Frankfurt waste disposal system consists of several components: a reusable system for take-away packaging with collection machines, a system with reusable packaging for food and drugstore supplies with an intelligent waste separation and collection system and a waste pipe system for residual waste disposal

Cost planning for the Frankfurt bridges at the upper end (8): Greening

Even in the luxury version of extensive green roofs, the greening of Frankfurt's bridges would only cost around 415 million euros - especially since large areas of the 1 million square meters of greenery on the bridges are also simply wild meadows or recreational meadows. Nevertheless, the estimate is significantly higher at 700 million euros, because extremely high-quality, research-relevant plant life is planned on the bridges. The revitalization of the plant life along the bridges is just as generous, estimated at around 100 million euros instead of 30 million euros: This is mainly due to the fact that the view of the bridges is to be significantly improved for residents.

Cost planning for the Frankfurt bridges at the upper end (9): Autonomous traffic

The centrally controlled traffic on Frankfurt's bridges, in which 400 autonomous vehicles are on the road, transporting up to 100,000 people a day and stopping at over 250 stops, is a relatively complex system, the cost of which per linear meter should be estimated at 8,000 euros.

The control center, which is a self-learning system, should also be estimated at 30 million euros above the normal expected costs for a center of this size.

Cost planning for the Frankfurt bridges in the middle range(9): Energy

When setting up the energy infrastructure of the energy-self-sufficient Brückenquartier, the estimate for the power grid including control system at 200 million euros is significantly higher than the usual estimate for a district with 30,000 inhabitants (more like 90-100 million euros): However, it must be taken into account here that this innovative, decentralized network must supply electricity not only to residents, but also to traffic.

In the case of thermal lines, PV modules and near-surface geothermal probes, however, the average estimates are used, since significant economies of scale and discount effects are indeed to be expected with such large quantities.

Cost planning for the Frankfurt bridges in the middle range(9): Water reservoir

The bathing lake being built in Niddapark is estimated to cost 18 million euros, almost twice as much as a normal bathing lake, as the integration into the surrounding area in a way that is compatible with nature conservation and the connection to the Nidda is to be designed as effectively as possible.

The construction of the infiltration shafts, however, is a process that has already been tried and tested in the Frankfurt city forest and is not expected to produce any surprises in other areas close to the city, which is why an average cost range of 2000 euros per square meter can be estimated here. However, the costs for the cisterns that will be installed under the roadway, which will have to be replaced as part of the bridge construction anyway, are still higher at .5000 euros per linear meter, as the connection to supply lines from properties along the bridges must also be taken into account.

Cost planning for the Frankfurt bridges in the middle area(9): Water pipe system

Even though “smart city water systems” are likely to become more widespread in the coming years and thus corresponding systems and modules more common and cheaper, the ring pipeline of the Frankfurt bridges and its components are still estimated to cost slightly more than average at 3,000 euros per linear meter.

The cleaning containers, on the other hand, are a standard product for all types of water to be treated, so that an average value of 150,000 euros per container is justified here.

The total cost estimate for the Frankfurt bridges is around 28 billion euros – with a buffer of over 15 percent of the estimated 33 billion euros investment volume that must be raised for the ESG project