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

Melvin and the data layers currently exist only for plans in the Netherlands, and GRB only for Belgium. On a United States plan these switches are missing. That is intended.

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

Use it when a toggle is gray, 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-us). This page assumes **Opening Map Environment...** is already gone.

## Melvin (Netherlands)

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

It is available on Dutch traffic plans and event plans. On event plans, set **Start** and **End**, including their times, in the header. The end must be later than the start. The control is disabled while exporting. [Event map layers](/hc/test/articles/event-map-layers-us).

1. Set complete **Start** and **End** (date and **hh:mm** on each side). Until then, the **MELVIN** control stays disabled and its tooltip reads **Fill in a date to use this option**.
2. Pan to a location in the **Netherlands**.
3. Click **MELVIN** in the header. It flips from **MELVIN OFF** to **MELVIN ON**.
4. Wait for the overlay, then pan to the works area.

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

The control only appears for Dutch plans. A Belgian **Country** will not show **MELVIN** at all.

## 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 center 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 catalog. |
| **Hectometer points (RWS)** missing | **The hectometer points 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 modeled 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 catalog 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-us).

## What good looks like

**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. To explain a layer on a traffic PDF, add it in **Items** → **PDF legend**, under **Map data**: [Traffic plan legend](/hc/test/articles/traffic-plan-legend-us).

## Next click

| You see | Do this |
|---------|---------|
| **Fill in a date to use this option** | Set **Start** and **End**, including **hh:mm**. |
| **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 check **TopoRD (Netherlands only)**. |
| **The hectometer points 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-us). Editor chrome: [Tour of the traffic plan editor](/hc/test/articles/editor-tour-us).