diff --git a/src/ai/api/ai_sign.hpp b/src/ai/api/ai_sign.hpp
new file mode 100644
--- /dev/null
+++ b/src/ai/api/ai_sign.hpp
@@ -0,0 +1,96 @@
+/* $Id$ */
+
+/** @file ai_sign.hpp Everything to query and build signs. */
+
+#ifndef AI_SIGN_HPP
+#define AI_SIGN_HPP
+
+#include "ai_object.hpp"
+#include "ai_error.hpp"
+#include "ai_company.hpp"
+
+/**
+ * Class that handles all sign related functions.
+ */
+class AISign : public AIObject {
+public:
+	static const char *GetClassName() { return "AISign"; }
+
+	/**
+	 * All sign related error messages.
+	 */
+	enum ErrorMessages {
+
+		/** Base for sign building related errors */
+		ERR_SIGN_BASE = AIError::ERR_CAT_SIGN << AIError::ERR_CAT_BIT_SIZE,
+
+		/** Too many signs have been placed */
+		ERR_SIGN_TOO_MANY_SIGNS,             // [STR_2808_TOO_MANY_SIGNS]
+	};
+
+	/**
+	 * Gets the maximum sign index; there are no valid signs with a higher index.
+	 * @return The maximum sign index.
+	 * @post Return value is always non-negative.
+	 */
+	static SignID GetMaxSignID();
+
+	/**
+	 * Checks whether the given sign index is valid.
+	 * @param sign_id The index to check.
+	 * @return True if and only if the sign is valid.
+	 */
+	static bool IsValidSign(SignID sign_id);
+
+	/**
+	 * Set the name of a sign.
+	 * @param sign_id The sign to set the name for.
+	 * @param name The name for the sign.
+	 * @pre IsValidSign(sign_id).
+	 * @pre 'name' must have at least one character.
+	 * @pre 'name' must have at most 30 characters.
+	 * @exception AIError::ERR_NAME_IS_NOT_UNIQUE
+	 * @return True if and only if the name was changed.
+	 */
+	static bool SetName(SignID sign_id, const char *name);
+
+	/**
+	 * Get the name of the sign.
+	 * @param sign_id The sign to get the name of.
+	 * @pre IsValidSign(sign_id).
+	 * @return The name of the sign.
+	 */
+	static const char *GetName(SignID sign_id);
+
+	/**
+	 * Gets the location of the sign.
+	 * @param sign_id The sign to get the location of.
+	 * @pre IsValidSign(sign_id).
+	 * @return The location of the sign.
+	 */
+	static TileIndex GetLocation(SignID sign_id);
+
+	/**
+	 * Builds a sign on the map.
+	 * @param location The place to build the sign.
+	 * @param text The text to place on the sign.
+	 * @pre AIMap::IsValidTile(location).
+	 * @pre 'text' must have at least one character.
+	 * @pre 'text' must have at most 30 characters.
+	 * @exception AISign::ERR_SIGN_TOO_MANY_SIGNS
+	 * @return The SignID of the build sign (use IsValidSign() to check for validity).
+	 *   In test-mode it returns 0 if successful, or any other value to indicate
+	 *   failure.
+	 */
+	static SignID BuildSign(TileIndex location, const char *text);
+
+	/**
+	 * Removes a sign from the map.
+	 * @param sign_id The sign to remove.
+	 * @pre IsValidSign(sign_id).
+	 * @return True if and only if the sign has been removed.
+	 */
+	static bool RemoveSign(SignID sign_id);
+};
+
+#endif /* AI_SIGN_HPP */