The Overlaat Bridge gets a companion

In 2026, the Overlaatbrug theme will be the last one that hasn't been further expanded since its inception in 2012. It's also a rock-solid bridge, which sets requirements for any potential expansion. We generally look for connections within the themes. For example, buildings that are often located together on the same street, or items like telephone booths and bus shelters that weren't always present in the same street, but were frequently seen in a city. But these elements also complement each other within the themes. Therefore, for the Overlaatbrug, we're looking for a bridge that preferably has a more or less similar year of construction, but above all proves to be physically compatible with the Overlaatbrug, creating added value. That has proven to be a significant search. But we think we've found a good companion.

Overveen is part of the municipality of Bloemendaal and is actually located pretty much right next to the center of Haarlem. If you travel from Haarlem station to Zandvoort, you'll cross the second bridge/viaduct within 1 km. Both bridges/viaducts were built after Haarlem's railway plan was laid out on a raised embankment, around 1905. This involved crossing waterways in several places. Necessity was turned into a virtue by also bridging a traffic artery at both locations. Otherwise, the two real life bridges in Haalem have little in common. So let's focus on the one we've modeled by Markenburg.

The Julianalaan railway bridge is a special example. With (truss) bridges in general, it's common to consider various forces, some of which are absorbed by cross-braces. These cross-braces, sometimes also called wind bracing, are characterized by their diagonal placement. This creates triangles in the structure. Triangles can be stronger and more rigid than a rectangle. However, these cross-braces also require materials, labor during construction, and maintenance. And they weigh quite a bit, which, of course, also has to be supported by the same bridge. Around 1900, the Leuven chief engineer Arthur Vierendeel devised an interesting alternative. He made the corners of the squares and rectangles in the bridge rigid. This reduced or even eliminated the need for cross-braces. Construction is a traditional sector, so this new invention was initially only used sporadically. However, the bridge over Julianalaan in Overveen quickly became a prime example.

In Overveen, we see an avenue and a canal, both spanned by the railway line. It is a double-track line, with each track having its own girder. Both girders have an inspection path on the outside, which, based on the current construction, was added later. The 3.6m clearance under the bridge was sufficient around 1900. But after 1950, trucks, in particular, became somewhat taller. Nowadays, a clearance of 4 meters is desirable. However, bridges and viaducts like this are difficult, or only very expensive, to adapt. Therefore, if heavy traffic can reach its destination by other means, bridges like this remain untouched. The abutments are elegantly constructed with brickwork and natural stone elements. They also feature retaining walls that ensure the embankment remains perfectly leveled. Various fences have stood on these triangular walls to prevent unauthorized persons from accessing the railway line. The current fencing model is meticulously crafted with thematic details.

Markenburg always strives to recreate an object, such as the bridge in this case, as completely and authentically as possible in a model. We're quite adept at it, if we say so ourselves. Because we only allow ourselves to be influenced when it proves physically impossible. Take the fence we mentioned earlier: If we literally scale it to 1:160, numerous components appear that are narrower or smaller than 0.1 mm. This creates a tension between components that are physically and financially impossible to reproduce. Will they also remain intact when touched or even shipped? And we haven't even mentioned whether details of 0.1 mm are still visible when placed halfway along a model railway. Or whether they can be assembled by the model builder. But at Markenburg, we still find it fun and inspiring to push the boundaries of what is feasible. Working out the brickwork down to the last detail, perfectly depicting the rivets in the corrugated steel, accurately replicating the structural shapes, and then also ensuring that the bridge can be used properly functionally in the model. And so on. Hopefully, some of that care is visible and will inspire fellow model builders.

The Overlaatbrug is a (potentially) large bridge because numerous spans can be easily and realistically placed one after the other on piers. A bridge measuring over 800 meters in length has existed between Waalwijk and Drunen. However, the girders are relatively compact, at 16.5 meters each. The bridge over Julianalaan in Overveen is slightly longer per span, with girders measuring 19.5 meters in length. But there are no piers in this situation, and the abutments, with a clearance height of 3.60, are almost a meter lower than the abutments and piers of the Overlaat Bridge. We could say, "That's a big difference," but we can also say positively that the bridges complement each other beautifully in form and function. But what makes the bridges good companions is that the bridge in Overveen has girders that are very similar in profile to the girders of the Overlaat Bridge. This means that the girders are interchangeable in design. The fact that the bridges were built during the same 25-year period and also share similar architectural styles also helps make it easy to swap out the girders. So, if you'd like the 4.5-meter height, to scale, of the Overlaat Bridge, but prefer to use the length of the girders of the Julianalaan Bridge, you can easily do so. The inspection path of the Juliana Bridge girders could perhaps be trimmed slightly when connecting to the Overlaat Bridge abutments to ensure a perfect fit, but this can also be handled effectively in various realistic ways. Together, the bridges offer a wide range of possibilities in terms of height, length, width, and various details. And all this while maintaining a convincingly realistic overall appearance. Even during the development of the Julianalaan Bridge, many of the cross-application possibilities were running through our minds. We are already curious to see which of the many possibilities will be most frequently applied.

Find here: theme Overlaat Bridge, with both bridges and accessories.