This page turns on **Melvin** and other optional map layers, or explains why they stay empty.

![Select map open on a Dutch plan — Traffic signs (NDW), BGT objects, Show Melvin in the header](https://hel1.your-objectstorage.com/traffic-chart-tutorials/helpcenter/en/traffic-plans/layers/02-select-map-panel.png)

Use it when a toggle is grey, the overlay is blank, or a basemap looks wrong. Missing layer data does **not** block you from drawing signs. Your placed objects remain the plan of record.

If the whole map is white, fix that first: [Map will not load or stays blank](/hc/test/articles/map-will-not-load). This page assumes **Opening Map Environment...** is already gone.

## Melvin (Netherlands)

**Melvin** is optional Dutch roadworks context. It needs both plan dates.

1. Set complete **Start date** and **End date** (date and time). Until then, **Show Melvin** stays disabled: **Fill in a date to use this option**.
2. Pan to a location in the **Netherlands**.
3. Click **Show Melvin** in the header (it becomes **Hide Melvin** when on).
4. Wait for the overlay, then pan to the works area.

An empty Melvin overlay can be correct: no overlapping roadworks for that time and place.

The button only appears for Dutch plans. A Belgian **Country** will not show **Show Melvin**.

## Other layers

Open **Select map** on the map tools. Availability depends on location, zoom, and configuration. Locked layers show a tooltip, often **This layer is locked**. Clicking a locked object can toast the same line.

| Symptom | Try this |
|---------|----------|
| Layer empty | **Zoom in**. Many layers have a minimum scale. |
| **Fire hydrants (BGT)** empty | Zoom in further. Tooltip: **Zoom in further to display fire hydrants.** |
| **BGT objects** empty | Zoom in. The panel says **Zoom in further to show BGT objects.** Use **Configure BGT objects** if you need specific classes. **Select all** / **Clear all** / **Done**. Toggles: **Layer visible**, **Enabled** / **Disabled**. |
| **TopoRD (Netherlands only)** missing | The map centre must be in the Netherlands. Tooltip: **Only available when the map center is in the Netherlands.** |
| **GRB (Flanders)** empty | Use it on a Belgian / Flanders location. Coverage is not nationwide. If the control is missing, the plan **Country** is probably not Belgium. |
| **Traffic signs (NDW)** empty | Zoom closer. NDW is existing-sign context, not your catalogue. |
| **Hectometer points (RWS)** missing | **The Rijkswaterstaat layer is temporarily unavailable.** Try later. |
| **Sewer system (GWSW)** empty | Zoom to about 1:10,000. Coverage varies by municipality. |
| **Heat & heat stress** unclear | Read **About the heat-stress map**. It is a modelled summer afternoon, not a live thermometer. |
| Basemap wrong | In **Select map**, pick **Cartographic**, **Hybrid**, **Light Gray**, or the fallback **Map**. |

**BGT does not specify whether a container is underground.** Treat hydrants and cabinets as context. Your placed signs remain the plan of record.

**Traffic signs (NDW)** are existing roadside plates in the Dutch register. They are not your catalogue and they do not go on the **Materials list**. Place your own signs from **Traffic Objects** → **Signs**.

Supplemental layers vary by municipality. Empty is often coverage, not a defect.

Event plans use a shorter **Select map**: **NDW Signs**, **Fire hydrants (BGT)**, **TopoRD (Netherlands only)**. Same zoom rules. Event hydrant tooltip: **Zoom in further to display fire hydrants.** Those layers do not place event objects. [Event map layers and hydrants](/hc/test/articles/event-map-layers).

## What good looks like

**Show Melvin** is clickable after both dates are set. The overlay appears where Melvin has data. Other checkboxes in **Select map** behave as the tooltips describe. **Map information** can still list visible layer types on a PDF legend page.

## Next click

| You see | Do this |
|---------|---------|
| **Fill in a date to use this option** | Set **Start date** and **End date**, including the time. |
| **Zoom in further to show BGT objects.** | **Zoom in**, then reopen **Configure BGT objects**. |
| **Zoom in further to display fire hydrants.** | **Zoom in** over Utrecht (or the works). |
| **Only available when the map center is in the Netherlands.** | **Search address** to a Dutch place, then tick **TopoRD (Netherlands only)**. |
| **The Rijkswaterstaat layer is temporarily unavailable.** | Leave **Hectometer points (RWS)** off and draw without it. |
| **This layer is locked** | **Unlock layer** in **Layers & Objects**, or leave it locked if you meant to freeze it. |
| **GRB (Flanders)** missing | Check plan **Country** is Belgium. |

## If it still fails

You can keep drawing. Full layer guide: [Map layers and Melvin](/hc/test/articles/map-layers-and-melvin). Editor chrome: [Tour of the traffic plan editor](/hc/test/articles/editor-tour).