Test Before Closing
Complete all test runs before the tunnel and mountain shell are permanently closed.
Reliable hidden track, realistic portals and permanent access
Build Model Railway Tunnels: Plan Portals, Clearance and Access
A convincing model railway tunnel begins with reliable track, sufficient clearance and safe maintenance access. Test long vehicles, curves and pantographs first. Then add the tunnel tube, inner walls, portal, removable mountain shell and realistic scenery.
A visible scenic feature and a hidden railway route
What Does a Reliable Model Railway Tunnel Require?
Building a model railway tunnel begins with the track rather than the portal. The hidden route must safely accommodate every intended locomotive, long coach, multiple unit and, where applicable, raised pantograph. Only after this has been confirmed should the tunnel tube, inner walls, portal, mountain shell and vegetation be added.
A tunnel fulfils several functions. It allows trains to disappear into the landscape, separates different layout scenes and can visually calm a tightly curved route. At the same time, it creates an area that is difficult to inspect and must remain accessible for cleaning, repairs and the recovery of derailed vehicles.
A visible tunnel entrance consists of more than a portal front. Wing walls, a short section of tunnel lining, drainage, rock or an earth slope and a clean transition to the track bed create a convincing overall scene. A brightly lit layout room or uncovered wooden framework should not be visible behind the portal.
Allow for Overhang
Keep the wide vehicle body and the overhanging ends clear on every curved section.
Remain Accessible
Hidden track must remain reachable for cleaning, inspection and vehicle recovery.
Embed the Portal
Connect the portal visibly to wing walls, rock, soil and the lined tunnel interior.
Five connected construction areas
A Model Railway Tunnel Is a Complete System
Track Base
A stable track support, reliable rail joints and sufficient power feeds form the technical foundation.
Clearance
Vehicles, curved overhang, roof fittings and overhead-line equipment require free space along the complete route.
Tunnel Interior
A tube, inner walls and a dark background prevent an open layout framework from being visible.
Portal
The opening, wing walls and masonry connections create the visible architectural entrance.
Landscape
Mountain surfaces, rocks, soil, scree and vegetation connect the structure to the surrounding scenery.
From a short underpass to a hidden mountain route
Which Type of Tunnel Suits the Model Railway Layout?
The tunnel length, number of tracks, location of curves, railway era and landscape determine whether a single portal, a ready-made tunnel or a completely scratch-built tube is most suitable.
Individual Tunnel Portal
The portal forms the visible entrance. The mountain shell, interior lining and hidden route are built individually and can be adapted precisely to the track plan.
Straight Ready-Made Tunnel
A compact solution for small layouts and dioramas. Internal dimensions, track position and maintenance access must be tested before permanent installation.
Corner Tunnel
A corner tunnel conceals a curved route at the edge of a layout while using little space. Lateral clearance requires particular attention because of vehicle overhang.
Single- or Double-Track Main Tunnel
A double-track portal requires the correct track centres. Two separate bores can be a convincing alternative for mountain routes and modern railway themes.
Narrow-Gauge and Light-Railway Tunnel
H0m, H0e, H0f, Nm and TTe represent smaller prototype profiles. The portal and interior must nevertheless provide sufficient curve clearance and maintenance access.
Modern Concrete or High-Speed Tunnel
Smooth concrete surfaces, large cross-sections, safety walkways and modern overhead-line equipment suit main lines and high-speed routes of recent eras.
Check vehicle movement rather than only the outside dimensions
Plan Clearance, Curves and Overhead Lines Inside the Tunnel
The portal opening alone does not prove that every train can pass safely. The decisive factor is the free space around the track, vehicle and pantograph throughout the complete tunnel route.
| Planning Area | What Must Be Checked? | Practical Test |
|---|---|---|
| Straight Track | Vehicle width, vehicle height, roof fittings and lateral access. | Move the largest intended vehicle slowly through a full-size portal template. |
| Track on a Curve | Overhang at the vehicle ends and inward movement at the vehicle centre. | Push and pull the longest bogie coach through the curve in both directions. |
| Narrow Gauge | Correct profile for H0m, H0e, Nm, TTe or another model gauge. | Select the narrow-gauge portal together with the dimensions of the intended vehicles. |
| Overhead Line | Contact-wire height, pantographs, supports and tunnel overhead-line construction. | Test with the pantograph fully raised or limited to its intended operating height. |
| Double-Track Route | Track centres, two long vehicles passing and the position of the side walls. | Position the two longest coaches simultaneously in the portal and curved section. |
| Portal Position | Curve radius, vehicle overhang and the visible tunnel interior. | Place the portal on straight track or a generous curve wherever possible. |
| Maintenance Space | Reach height, track cleaning, cable access and vehicle recovery. | Provide a removable mountain, rear opening or sufficiently large access hatch. |
The actual vehicle, selected radius, track system, portal opening and overhead-line equipment remain authoritative. A general clearance dimension cannot replace a practical test run.
Portals on Tight Curves Require Additional Lateral Space
The ends of a long coach can project beyond the outside of the track profile while the centre of the coach moves inward. Test the longest intended coach rather than only a short locomotive.
Connect the portal front visibly to the mountain shell
Design the Tunnel Portal, Interior Walls and Landscape Realistically
The construction and surface of the portal should suit the represented railway, era and region. A lined visible interior prevents the portal from looking like a flat scenic façade.
Natural Stone and Rubble Masonry
Natural-stone portals suit branch lines, mountain routes and older main lines. Joints, individual stains and an irregular transition into the mountain make the entrance more convincing.
Brick, Concrete and Modern Forms
Brick portals support industrial and urban themes. Concrete portals suit upgraded main lines, newly built tunnels and modern railway scenes.
Visible Tunnel Tube
Straight or curved inner walls line the area immediately behind the portal. A dark progression or gentle curve prevents a direct view into the open layout framework.
Wing Walls and Drainage
Walls visually retain the slope. Scree, a drainage channel, cable trough and a clean transition to the ballast make the tunnel entrance understandable.
Weathering Around the Portal
Dark areas above the opening, moisture traces in the joints and restrained vegetation suggest use and exposure. A uniformly black surface usually looks artificial.
Removable Mountain Connection
A fine separation line can be concealed behind rock, a wall, bush or terrain edge. Locating pins or magnets return the removable landscape section to the correct position.
Select the tunnel profile by scale and model track gauge
Model Railway Tunnels for Standard- and Narrow-Gauge Railways
The visible scale determines the size of the masonry and portal. The model track gauge additionally determines which vehicle profile must pass through the opening.
| Gauge | Typical Scale | Typical Model Track Gauge | Tunnel-Building Consideration |
|---|---|---|---|
| Z | 1:220 | 6.5 mm | Fine portals and small tunnel tubes still require an access opening that can be reached safely. |
| N and Nm | 1:160 | 9 mm or a narrower model gauge | Long vehicles create extensive landscape effects but require sufficient clearance on curves. |
| TT, TTm and TTe | 1:120 | 12 mm or a narrow-gauge variant | Select the portal explicitly for the intended TT or narrow-gauge profile. |
| H0 | 1:87 | 16.5 mm | A large selection of single- and double-track portals, interior walls and ready-made tunnels is available. |
| H0m, H0e and H0f | 1:87 | 12, 9 or 6.5 mm | The scenery remains H0-sized, while the narrower railway profile requires a suitably proportioned portal. |
| S, Sm and Se | 1:64 | 22.5 mm or a narrow-gauge variant | Portals and inner tubes are frequently constructed individually for the particular project. |
| 0, 0m and 0e | Usually approximately 1:45 | 32 mm or a narrow-gauge variant | Plan the large portal opening and wide maintenance access at an early stage. |
| 1, Im and Ie | 1:32 | 45 mm or a narrow-gauge variant | Tunnel shells are usually built in lightweight, stable and removable sections. |
| G, II and IIm | Prototype-dependent, frequently approximately 1:22.5 | Frequently 45 mm | Outdoor tunnels must be weather-resistant, drained and permanently accessible for inspection and cleaning. |
Track gauge, scale and clearance are separate considerations. Always test the selected portal with the actual vehicles intended for operation.
Portals, tubes and scenery materials
Manufacturers of Model Railway Tunnels and Tunnel Entrances
Portals, inner walls, ready-made tunnels, retaining walls and scenery materials from different manufacturers can be combined when the scale, opening and selected construction materials are compatible.
Portals, ready-made tunnels, corner tunnels and inner walls
Tunnel Products Directly from Modellbahnshop
Filter the verified selection by gauge, manufacturer, number of tracks, application and product group. Every product card leads directly to the English version of the corresponding product page.
NOCH · H0 · Double-Track Portal
NOCH 58052 PROFI-plus
Natural-stone portal for a double-track H0 tunnel entrance.
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NOCH · H0 · Single-Track Portal
NOCH 58051 PROFI-plus
Classic single-track portal for an H0 main line or branch line.
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FALLER · H0 · Double-Track Portal
FALLER 120578 Tunnel Portal
Portal kit for a broad H0 main-line tunnel opening.
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NOCH · H0m/H0e · Narrow Gauge
NOCH 58026 Narrow-Gauge Portal
Rubble-stone portal for metre-gauge and narrower H0 railways.
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NOCH · H0 · Curved Inner Walls
NOCH 58031 Tunnel Interior Walls
Lining for the visible interior section of a tunnel on a curve.
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FALLER · H0 · Tunnel Tube
FALLER 170862 Tunnel Tube
Formable rock texture for individual tunnel interior surfaces.
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NOCH · H0 · Straight Ready-Made Tunnel
NOCH 02200 Ready-Made Tunnel
Compact tunnel body for a straight single-track H0 route.
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NOCH · H0 · Corner Tunnel
NOCH 05130 Corner Tunnel
Ready-made landscape form for concealing an H0 corner curve.
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Auhagen · TT · Single-Track Portals
Auhagen 13276 Tunnel Portals
Two portals for TT routes with steam or electric operation.
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NOCH · N · Double-Track Portal
NOCH 34852 Stone-Wall Portal
Compact stone portal for a double-track N-gauge route.
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Auhagen · N · Single-Track Portals
Auhagen 44635 Tunnel Portals
Portals for straight or curved single-track N-gauge entrances.
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FALLER · Z · Tunnel Tube
FALLER 282960 Tunnel Tube
Structured interior lining for compact Z-gauge tunnels.
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Busch · G · Two Tunnel Portals
Busch 8610 Tunnel Portals
Large-format portals for garden railways and large-scale scenery.
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FALLER · H0 · Steam & Overhead Line
FALLER 120559 Tunnel Portal
Large portal opening for different types of H0 railway operation.
View Product →Select the Portal and Track Together
Check the gauge, number of tracks, curve radius, longest vehicle and overhead-line requirements before permanently installing the portal, tunnel tube and mountain.
Tunnels and Portals
Tunnel portals, ready-made tunnels, inner walls and tunnel tubes.
Walls and Building Boards
Wing walls, structural sheets, hard foam and surface materials.
Plaster and Filler
Materials for mountain transitions, rocks and portal edges.
Bridges and Viaducts
Railway structures for valleys, underpasses and mountain routes.
Track and Turnouts
The technical foundation of the visible and hidden railway route.
Overhead Lines
Contact wire, masts and components for electric train operation.
Adhesives
Adhesives for hard foam, plastic, wood and landscape materials.
Paint and Weathering
Colour joints, soot, moisture traces, masonry and surrounding rock.
From tested track to a completed tunnel entrance
Build a Model Railway Tunnel in Eight Steps
This construction sequence keeps the hidden route open for as long as possible and separates technical testing, interior construction and landscape design.
Define the Tunnel Route
Planning
Draw the portal, track and mountain contour together
Determine the tunnel entrance, hidden route, possible access openings and transition into the surrounding landscape.
Test the Complete Vehicle Profile
Clearance
Use the longest coach and highest roof equipment
Test both directions, pushed trains, passing vehicles and, where applicable, the intended pantograph position.
Build a Reliable Track Base
Track Construction
Create a stable support and several power feeds
The track, rail joiners and wiring must operate reliably before any permanent landscape construction begins.
Prepare the Maintenance Access
Accessibility
Size the opening before constructing the mountain
The opening must permit track cleaning, repairs and the safe removal of the longest intended vehicle.
Dry-Fit the Portal
Tunnel Entrance
Align the track centre and opening precisely
Before applying adhesive, check the vehicle clearance, wing walls and transition between the portal and mountain.
Line the Tunnel Interior
Tunnel Tube
Add straight or curved interior walls
Give the area visible through the portal a dark, structured surface that matches the selected portal.
Close the Mountain Removably
Landscape Construction
Position separation lines outside the main viewing area
Rigid foam, mesh or a lightweight framework forms the mountain shell without blocking the maintenance route.
Weather the Portal and Surroundings
Final Detailing
Combine rock, scree and vegetation sparingly
After a final test run, add joint colour, operational staining, soil, rock fragments and suitable plants.
Keep hidden track permanently accessible
Maintain Tunnel Routes and Avoid Typical Construction Mistakes
Dust, abrasion and small remains of scenery material also collect on hidden track. The tunnel therefore requires an unobstructed cleaning route. Loose plaster fragments, scatter material and cables must not hang above the track.
Turnouts and complicated track connections should preferably not be positioned beneath a fixed mountain. When this cannot be avoided, the complete area must remain accessible from above, below or behind.
A simple service light or camera can make inspection easier but cannot replace a physical access opening. Garden-railway tunnels additionally require drainage, frost-resistant construction and protection against leaves and other outdoor debris.
Testing the Portal Only with a Short Locomotive
The longest coach determines the lateral space required on a curved route.
Closing the Mountain Without a Recovery Opening
Every hidden location must remain safely reachable by hand.
Planning the Overhead Line Afterwards
Contact wire, pantographs and tunnel supports require additional height and maintenance access.
Showing a Bright Layout Room Behind the Portal
An inner wall, dark screen or curved route creates convincing visual depth.
Carry Out Test Runs After Every Construction Phase
The portal, inner walls, overhead-line equipment and removable mountain can alter previously available space. Test the complete train formation again after every significant construction step.
Answers about portals, curves, interiors and access
Frequently Asked Questions About Building Model Railway Tunnels
These answers cover portal dimensions, track position, overhead lines, narrow-gauge tunnels, maintenance access and realistic landscape design.
How Wide and High Must a Model Railway Tunnel Be?
This depends on the scale, vehicle profile, curve radius, track centres and overhead-line equipment. Test the portal and tunnel tube with the largest vehicles that will actually be used.
Can a Tunnel Portal Stand Directly on a Curve?
Yes, provided additional lateral clearance is available. Straight track or a generous curve is generally safer and often more prototypical.
How Is Vehicle Overhang Tested Inside a Tunnel?
Push and pull the longest coach slowly through the curve. Neither its ends nor its centre may touch the portal or inner walls.
What Must Be Considered for an Overhead Line in a Tunnel?
Contact-wire height, pantographs and supports require additional space. Test the pantograph in the intended operating position before closing the tunnel.
How Far Should a Tunnel Interior Wall Extend?
At least the area visible from the normal viewing position should be lined. A dark progression prevents the open framework and cables from being visible.
How Large Should a Maintenance Opening Be?
It must permit the longest vehicle to be gripped and removed safely while also providing access to the track, cables and any turnouts.
Can a Turnout Be Positioned Inside a Tunnel?
Only when it remains completely accessible. A position outside the fixed mountain shell or beneath a clearly removable section is preferable.
Is a Ready-Made Tunnel or a Scratch-Built Tunnel Better?
Ready-made tunnels can be installed quickly. A scratch-built tunnel can be adapted more precisely to the track plan, radius, landscape and maintenance access.
Does a Short Tunnel Require a Complete Inner Tube?
Not necessarily. The visible area should nevertheless be lined and the background made sufficiently dark that no open framework remains visible.
Which Tunnel Portals Suit H0m and H0e?
Both use the 1:87 scenery scale but represent narrow-gauge profiles. Dedicated narrower portals and matching interior components are available.
Can a Tunnel Conceal a Tight Curve?
Yes. The curve must still provide reliable running, adequate lateral clearance and full internal access for maintenance.
How Can Tunnel Track Be Kept Clean Permanently?
An accessible opening, low-dust scenery work and regular track cleaning are more important than a completely sealed tunnel tube.
Plan Reliable Operation First, Then Design the Tunnel
Check the track, clearance, overhead line and maintenance access. Then complete the entrance with a suitable portal, inner walls, removable mountain shell and realistic vegetation.
Content reviewed and updated on 16 August 2026. Product dimensions, vehicle data, track geometry and each manufacturer’s processing instructions remain authoritative.