diff --git a/gtfs.js b/gtfs.js
index ba81f95..edbb0c2 100644
--- a/gtfs.js
+++ b/gtfs.js
@@ -9,7 +9,7 @@ const forEachWithLog = require('./helpers/logging_iterator_wrapper');
 const { exportGtfs } = require('./helpers/export');
 const getters = require('./helpers/getters');
 const { importTable } = require('./helpers/import');
-const schema = require('./helpers/schema');
+const defaultSchema = require('./helpers/schema');
 
 /**
  * Table-generic function to add items in a table of a GTFS.
@@ -24,7 +24,7 @@ function addItems(gtfs, tableName, items) {
   }
 
   const indexedTable = gtfs.getIndexedTable(tableName);
-  const indexKeys = schema.indexKeysByTableName[tableName];
+  const indexKeys = gtfs._schema.indexKeysByTableName[tableName];
 
   if (indexKeys.indexKey) {
     items.forEach(item => indexedTable.set(item[indexKeys.indexKey], item));
@@ -76,7 +76,7 @@ function forEachItem(gtfs, tableName, iterator) {
   }
 
   const indexedTable = gtfs.getIndexedTable(tableName);
-  const deepness = schema.deepnessByTableName[tableName];
+  const deepness = gtfs._schema.deepnessByTableName[tableName];
 
   if (deepness === 1) {
     forEachWithLog(`Iterating:${tableName}`, indexedTable, (item) => {
@@ -105,7 +105,7 @@ function removeItems(gtfs, tableName, items) {
   }
 
   const indexedTable = gtfs.getIndexedTable(tableName);
-  const indexKeys = schema.indexKeysByTableName[tableName];
+  const indexKeys = gtfs._schema.indexKeysByTableName[tableName];
 
   if (indexKeys.indexKey) {
     items.forEach(item => indexedTable.delete(item[indexKeys.indexKey]));
@@ -133,7 +133,7 @@ function removeItems(gtfs, tableName, items) {
  * @param  {Object|Map} indexedItems Object properly indexed as the schema requires the table to be (see schema.js).
  */
 function setIndexedItems(gtfs, tableName, indexedItems) {
-  if (indexedItems instanceof Map === false && schema.deepnessByTableName[tableName] !== 0) {
+  if (indexedItems instanceof Map === false && gtfs._schema.deepnessByTableName[tableName] !== 0) {
     throw new Error(`indexedItems must be a Map instead of: ${indexedItems}`);
   }
 
@@ -165,18 +165,28 @@ class Gtfs {
    *   }]
    * };
    *
+   *
    * # options.throws
    *
    * Optional ad-hoc boolean. Default is true. Will force the parser to ignore invalid rows in the tables.
    *
+   * # options.forcedSchema
+   *
+   * Will overwrite the default schema by the value passed.
+   *
+   *
    * @param {string} [path] Path to the folder that contains the GTFS text files.
    * @param {{
    *   regexPatternObjectsByTableName: Map.<string, Array.<{regex: RegExp, pattern: string}>>,
-   *   throws: boolean
+   *   throws: boolean,
+   *   forcedSchema,
    * }} [options] Optional. See list above.
    * @return {Gtfs} gtfs Instanciated GTFS object.
    */
-  constructor(path, {regexPatternObjectsByTableName = new Map(), throws = true} = {}) {
+  constructor(
+    path,
+    { regexPatternObjectsByTableName = new Map(), throws = true, postImportTableFunction, forcedSchema } = {}
+  ) {
     if (path !== undefined) {
       if (typeof path !== 'string' || path.length === 0) {
         throw new Error(`Gtfs need a valid input path as string, instead of: "${path}".`);
@@ -194,7 +204,9 @@ class Gtfs {
     this._path = path;
     this._regexPatternObjectsByTableName = regexPatternObjectsByTableName;
     this._shouldThrow = throws;
+    this._postImportTableFunction = postImportTableFunction;
     this._tables = new Map();
+    this._schema = defaultSchema || forcedSchema;
   }
 
   /* Input/Output */
@@ -273,14 +285,21 @@ class Gtfs {
    *
    * @return {Set.<string>} Array of the table names
    */
-  getTableNames() { return new Set([...schema.tableNames, ...this._tables.keys()]); }
+  getTableNames() { return new Set([...this._schema.tableNames, ...this._tables.keys()]); }
+
+  /**
+   * Get the default schema of the GTFS. For safety, the schema is cloned before being passed.
+   *
+   * @return {Object} The schema
+   */
+  static getDefaultSchema() { return JSON.parse(JSON.stringify(defaultSchema)); }
 
   /**
-   * Get the schema of the GTFS. For safety, the schema is cloned before beeing passed.
+   * Get the schema of the GTFS. For safety, the schema is cloned before being passed.
    *
    * @return {Object} The schema
    */
-  static getSchema() { return JSON.parse(JSON.stringify(schema)); }
+  getSchema() { return JSON.parse(JSON.stringify(this._schema)); }
 
   /**
    * Build the list of the keys used in a table of the GTFS. Since the GTFS specification allows any additional field,
diff --git a/helpers/export.js b/helpers/export.js
index 62f1018..da0f33e 100644
--- a/helpers/export.js
+++ b/helpers/export.js
@@ -10,7 +10,6 @@ const errorLog = require('debug')('gtfsNodeLib:e');
 const fs = require('fs-extra');
 
 const { fromObjectToCsvString } = require('./csv');
-const schema = require('./schema');
 
 /**
  * Private functions
@@ -80,7 +79,7 @@ function exportTable(tableName, gtfs, outputPath, callback) {
       will be fixed.
       2015-03-10
     */
-    const deepness = schema.deepnessByTableName[tableName];
+    const deepness = gtfs._schema.deepnessByTableName[tableName];
 
     if (deepness === 0) {
       const row = fromObjectToCsvString(gtfs.getIndexedTable(tableName), keys);
diff --git a/helpers/getters.js b/helpers/getters.js
index 5b2eb4c..216bd16 100644
--- a/helpers/getters.js
+++ b/helpers/getters.js
@@ -1,6 +1,6 @@
 'use strict';
 
-const schema = require('./schema');
+/* eslint-disable no-underscore-dangle */
 
 /**
  * Build the list of the keys used in a table of the GTFS. Since the GTFS specification allows any additional field,
@@ -12,8 +12,8 @@ const schema = require('./schema');
  */
 function getActualKeysForTable(gtfs, tableName) {
   const getSample = iterable => ((iterable && iterable.values().next()) ? iterable.values().next().value : undefined);
-  const keys = [...schema.keysByTableName[tableName]];
-  const deepness = schema.deepnessByTableName[tableName];
+  const keys = [...gtfs._schema.keysByTableName[tableName]];
+  const deepness = gtfs._schema.deepnessByTableName[tableName];
   const table = gtfs.getIndexedTable(tableName);
   let sampleItem;
 
@@ -27,7 +27,7 @@ function getActualKeysForTable(gtfs, tableName) {
 
   if (sampleItem) {
     Object.keys(sampleItem).forEach((key) => {
-      if (schema.keysByTableName[tableName].includes(key) === false) {
+      if (gtfs._schema.keysByTableName[tableName].includes(key) === false) {
         keys.push(key);
       }
     });
@@ -57,15 +57,15 @@ function getGrandParentItem(itemWithForeignIndexId, parentTableName, grandParent
   ) {
     throw new Error(`itemWithForeignIndexId must be a plain object, instead of an "${typeof itemWithForeignIndexId}"`);
   }
-  if (schema.tableNames.includes(parentTableName) === false) {
+  if (gtfs._schema.tableNames.includes(parentTableName) === false) {
     throw new Error(`Cannot find table with name "${parentTableName}"`);
   }
-  if (schema.tableNames.includes(grandParentTableName) === false) {
+  if (gtfs._schema.tableNames.includes(grandParentTableName) === false) {
     throw new Error(`Cannot find table with name "${grandParentTableName}"`);
   }
 
   /* Reach parent item */
-  const parentIndexKey = schema.indexKeysByTableName[parentTableName].indexKey;
+  const parentIndexKey = gtfs._schema.indexKeysByTableName[parentTableName].indexKey;
 
   if (itemWithForeignIndexId[parentIndexKey] === undefined) {
     throw new Error(`itemWithForeignIndexId should contain the foreign index key "${parentIndexKey}"`);
@@ -78,7 +78,7 @@ function getGrandParentItem(itemWithForeignIndexId, parentTableName, grandParent
   }
 
   /* Reach grandparent item */
-  const grandParentIndexKey = schema.indexKeysByTableName[grandParentTableName].indexKey;
+  const grandParentIndexKey = gtfs._schema.indexKeysByTableName[grandParentTableName].indexKey;
 
   if (!parentItem[grandParentIndexKey]) {
     throw new Error(`parentItem should contain the foreign index key "${grandParentIndexKey}"${parentItem}`);
@@ -96,14 +96,14 @@ function getGrandParentItem(itemWithForeignIndexId, parentTableName, grandParent
  * @return {Map.<string, Object>} Indexed child items.
  */
 function getIndexedItemsWithParent(parentItem, tableName, gtfs) {
-  if (schema.deepnessByTableName[tableName] !== 2) {
+  if (gtfs._schema.deepnessByTableName[tableName] !== 2) {
     throw new Error(`Table "${tableName}" is not of deepness 2.`);
   }
   if (parentItem === undefined || parentItem === null || typeof parentItem !== 'object') {
     throw new Error(`Parent item should be a plain object, instead of an "${typeof parentItem}"`);
   }
 
-  const firstIndexKey = schema.indexKeysByTableName[tableName].firstIndexKey;
+  const firstIndexKey = gtfs._schema.indexKeysByTableName[tableName].firstIndexKey;
 
   if (parentItem[firstIndexKey] === undefined) {
     throw new Error(`Parent item should contain the foreign index key "${firstIndexKey}"`);
@@ -123,7 +123,7 @@ function getIndexedItemsWithParent(parentItem, tableName, gtfs) {
  * @return {Map.<string, Object>} Indexed child items.
  */
 function getIndexedItemsWithParentIndex(parentIndex, tableName, gtfs) {
-  if (schema.deepnessByTableName[tableName] !== 2) {
+  if (gtfs._schema.deepnessByTableName[tableName] !== 2) {
     throw new Error(`Table "${tableName}" is not of deepness 2.`);
   }
   if (typeof parentIndex !== 'string') {
@@ -146,7 +146,7 @@ function getIndexedItemsWithParentIndex(parentIndex, tableName, gtfs) {
  * @param {Gtfs}   gtfs      Gtfs object
  */
 function getItemWithIndex(index, tableName, gtfs) {
-  if (schema.deepnessByTableName[tableName] !== 1) {
+  if (gtfs._schema.deepnessByTableName[tableName] !== 1) {
     throw new Error(`Cannot access item with only one index in "${tableName}", since the deepness is not 1.`);
   }
   if (typeof index !== 'string') {
@@ -170,7 +170,7 @@ function getItemWithIndex(index, tableName, gtfs) {
  * @param {Gtfs}   gtfs        Gtfs object
  */
 function getItemWithIndexes(firstIndex, secondIndex, tableName, gtfs) {
-  if (schema.deepnessByTableName[tableName] !== 2) {
+  if (gtfs._schema.deepnessByTableName[tableName] !== 2) {
     throw new Error(`Cannot access item with two indexes in "${tableName}", since the deep is not 2.`);
   }
   if (firstIndex === undefined || firstIndex === null || typeof firstIndex !== 'string') {
@@ -202,7 +202,7 @@ function getParentItem(itemWithForeignIndexId, tableName, gtfs) {
     throw new Error(`itemWithForeignIndexId must be a plain object, instead of an "${typeof itemWithForeignIndexId}"`);
   }
 
-  const indexKey = schema.indexKeysByTableName[tableName].indexKey;
+  const indexKey = gtfs._schema.indexKeysByTableName[tableName].indexKey;
 
   if (itemWithForeignIndexId[indexKey] === undefined) {
     throw new Error(
diff --git a/helpers/import.js b/helpers/import.js
index 6e5efa8..2406ae5 100644
--- a/helpers/import.js
+++ b/helpers/import.js
@@ -7,7 +7,6 @@ const fs = require('fs-extra');
 
 const eachWithLog = require('./logging_iterator_wrapper');
 const { fromCsvStringToArray } = require('./csv');
-const schema = require('./schema');
 
 /**
  * Import a table in the GTFS.
@@ -17,7 +16,7 @@ const schema = require('./schema');
  */
 
 exports.importTable = (gtfs, tableName) => {
-  const indexKeys = schema.indexKeysByTableName[tableName];
+  const indexKeys = gtfs._schema.indexKeysByTableName[tableName];
   const fullPath = `${gtfs.getPath() + tableName}.txt`;
 
   if (fs.existsSync(fullPath)) {
diff --git a/package-lock.json b/package-lock.json
index 6278c85..edc073e 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -2,7 +2,6 @@
   "name": "@transit/gtfs",
   "version": "3.0.0",
   "lockfileVersion": 1,
-  "requires": true,
   "dependencies": {
     "acomb": {
       "version": "1.2.2",
@@ -1573,6 +1572,15 @@
       "integrity": "sha1-BOaSb2YolTVPPdAVIDYzuFcpfiw=",
       "dev": true
     },
+    "string_decoder": {
+      "version": "1.0.3",
+      "resolved": "https://registry.npmjs.org/string_decoder/-/string_decoder-1.0.3.tgz",
+      "integrity": "sha512-4AH6Z5fzNNBcH+6XDMfA/BTt87skxqJlO0lAh3Dker5zThcAxG6mKz+iGu308UKoPPQ8Dcqx/4JhujzltRa+hQ==",
+      "dev": true,
+      "requires": {
+        "safe-buffer": "5.1.1"
+      }
+    },
     "string-width": {
       "version": "1.0.2",
       "resolved": "https://registry.npmjs.org/string-width/-/string-width-1.0.2.tgz",
@@ -1584,15 +1592,6 @@
         "strip-ansi": "3.0.1"
       }
     },
-    "string_decoder": {
-      "version": "1.0.3",
-      "resolved": "https://registry.npmjs.org/string_decoder/-/string_decoder-1.0.3.tgz",
-      "integrity": "sha512-4AH6Z5fzNNBcH+6XDMfA/BTt87skxqJlO0lAh3Dker5zThcAxG6mKz+iGu308UKoPPQ8Dcqx/4JhujzltRa+hQ==",
-      "dev": true,
-      "requires": {
-        "safe-buffer": "5.1.1"
-      }
-    },
     "strip-ansi": {
       "version": "3.0.1",
       "resolved": "https://registry.npmjs.org/strip-ansi/-/strip-ansi-3.0.1.tgz",
diff --git a/tests.js b/tests.js
index 179347d..2fb8cde 100644
--- a/tests.js
+++ b/tests.js
@@ -669,11 +669,11 @@ describe('Tests on GTFS', () => {
     const funkyStop = {};
     gtfs.addStop(funkyStop);
 
-    expect(Gtfs.getSchema().keysByTableName.stops).to.deep.equal(gtfs.getActualKeysForTable('stops'));
+    expect(gtfs.getSchema().keysByTableName.stops).to.deep.equal(gtfs.getActualKeysForTable('stops'));
 
     funkyStop.route_funky_name = 'Tshboom tshboom';
     funkyStop.route_esoteric_float = 120.37;
-    const standardRouteKeys = Gtfs.getSchema().keysByTableName.stops;
+    const standardRouteKeys = gtfs.getSchema().keysByTableName.stops;
     const actualRouteKeys = gtfs.getActualKeysForTable('stops');
 
     expect(standardRouteKeys).to.not.deep.equal(actualRouteKeys);