diff --git a/lib/gtfs2connections.js b/lib/gtfs2connections.js
index 8224d84..a8b2c04 100644
--- a/lib/gtfs2connections.js
+++ b/lib/gtfs2connections.js
@@ -1,5 +1,6 @@
 const { Worker, isMainThread, parentPort, workerData } = require('worker_threads');
 const fs = require('fs');
+const zlib = require('zlib');
 const path = require('path');
 const ChildProcess = require('child_process');
 const del = require('del');
@@ -17,7 +18,6 @@ const Connections2Triples = require('./Connections2Triples');
 
 
 const readdir = util.promisify(fs.readdir);
-const appendFile = util.promisify(fs.appendFile);
 const exec = util.promisify(ChildProcess.exec);
 
 const numCPUs = require('os').cpus().length;
@@ -61,7 +61,6 @@ Mapper.prototype.resultStream = async function (path, output, done) {
       const worker = new Worker(__filename, {
          workerData: {
             instance: i,
-            path,
             output,
             options: this._options
          },
@@ -88,13 +87,14 @@ Mapper.prototype.resultStream = async function (path, output, done) {
                await removePrefixes(output);
                ext = 'ttl';
             } else if (format === 'ntriples') {
-               ext = 'n3';
+               ext = 'nt';
             }
 
             try {
                console.error('Merging final Linked Connections file...');
+               
                // Join all resulting files into one
-               await exec(`for i in ${raws.map(r => { return `${r}.${ext}` }).join(" ")} ; do cat "$i" >> linkedConnections.${ext} && rm "$i" || break ; done`, { cwd: output });
+               await exec(`for i in ${raws.map(r => { return `${r}.${ext}.gz` }).join(" ")} ; do zcat "$i" >> linkedConnections.${ext} && rm "$i" || break ; done`, { cwd: output });
                let t1 = new Date();
                console.error('linkedConnections.' + ext + ' File created in ' + (t1.getTime() - t0.getTime()) + ' ms');
                await del(
@@ -133,27 +133,34 @@ async function cleanUpSources(sources) {
 
 async function appendLineBreaks(output) {
    const files = (await readdir(output)).filter(raw => raw.startsWith('raw_'));
+   const promises = [];
    for (const [i, f] of files.entries()) {
       if (i < files.length - 1) {
-         await appendFile(`${output}/${f}`, '\n')
+         promises.push(exec(`echo "" | gzip >> ${f}`, { cwd: output }));
       }
    }
+
+   await Promise.all(promises);
 }
 
 async function removePrefixes(output) {
    const files = (await readdir(output)).filter(raw => raw.startsWith('raw_'));
+   const promises = [];
    for (const [i, f] of files.entries()) {
       if (i > 0) {
          // TODO: find a not hard-coded way to remove prefixes
-         await exec(`sed -i 1,4d ${f}`, { cwd: output });
+         promises.push(exec(`zcat ${f} | tail -n +4 | gzip > ${f}.temp && mv ${f}.temp ${f}`, { cwd: output }))
       }
    }
+
+   await Promise.all(promises);
 }
 
 // Code executed only on a Worker Thread
 if (!isMainThread) {
+   let fmt = 'json';
    // Read the connection rules file created in the master thread and build the Connection objects!
-   let connectionStream = fs.createReadStream(workerData['path'] + '/connections_' + workerData['instance'] + '.txt', { encoding: 'utf8', objectMode: true })
+   let connectionStream = fs.createReadStream(workerData['output'] + '/connections_' + workerData['instance'] + '.txt', { encoding: 'utf8', objectMode: true })
       .pipe(JSONLParser())
       .pipe(new ConnectionsBuilder())
       .on('error', function (e) {
@@ -166,8 +173,7 @@ if (!isMainThread) {
       if (format === 'mongo') {
          connectionStream = connectionStream.pipe(new Connections2Mongo());
       }
-      connectionStream = connectionStream.pipe(new JSONLStringer())
-         .pipe(fs.createWriteStream(workerData['output'] + '/raw_' + workerData['instance'] + '.json'));
+      connectionStream = connectionStream.pipe(new JSONLStringer());
    } else if (['jsonld', 'mongold'].includes(format)) {
       let context = undefined;
       // Only include the context for the first instance
@@ -194,35 +200,37 @@ if (!isMainThread) {
          connectionStream = connectionStream.pipe(new Connections2Mongo());
       }
       // Pipe the objects to a file
-      connectionStream = connectionStream.pipe(new JSONLStringer())
-         .pipe(fs.createWriteStream(workerData['output'] + '/raw_' + workerData['instance'] + '.json'));
+      connectionStream = connectionStream.pipe(new JSONLStringer());
    } else if (format === 'csv') {
+      fmt = 'csv';
       // Only include the header on the first file
       let header = false;
       if (workerData['instance'] === 0) {
          header = true;
       }
-      connectionStream = connectionStream.pipe(new Connections2CSV(header))
-         .pipe(fs.createWriteStream(workerData['output'] + '/raw_' + workerData['instance'] + '.csv'));
+      connectionStream = connectionStream.pipe(new Connections2CSV(header));
    } else if (format === 'turtle') {
+      fmt = 'ttl';
       let prefixes = {
          lc: 'http://semweb.mmlab.be/ns/linkedconnections#',
          gtfs: 'http://vocab.gtfs.org/terms#',
          xsd: 'http://www.w3.org/2001/XMLSchema#'
       };
       connectionStream = connectionStream.pipe(new Connections2Triples(workerData['options']['baseUris']))
-         .pipe(new N3.StreamWriter({ prefixes: prefixes }))
-         .pipe(fs.createWriteStream(workerData['output'] + '/raw_' + workerData['instance'] + '.ttl'));
+         .pipe(new N3.StreamWriter({ prefixes: prefixes }));
    } else if (format === 'ntriples') {
+      fmt = 'nt';
       connectionStream = connectionStream.pipe(new Connections2Triples(workerData['options']['baseUris']))
-         .pipe(new N3.StreamWriter({ format: 'N-Triples' }))
-         .pipe(fs.createWriteStream(workerData['output'] + '/raw_' + workerData['instance'] + '.n3'));
+         .pipe(new N3.StreamWriter({ format: 'N-Triples' }));
    }
 
    connectionStream.on('finish', () => {
       parentPort.postMessage('done');
    });
 
+   connectionStream.pipe(zlib.createGzip())
+      .pipe(fs.createWriteStream(`${workerData['output']}/raw_${workerData['instance']}.${fmt}.gz`));
+
 }
 
 module.exports = Mapper;
diff --git a/lib/stoptimes/st2c.js b/lib/stoptimes/st2c.js
index a991be5..8a475ac 100644
--- a/lib/stoptimes/st2c.js
+++ b/lib/stoptimes/st2c.js
@@ -25,7 +25,8 @@
 			 if (stopTime['arrival_time'] === '' && stopTime['departure_time'] === '') {
 				 // Both arrival and departure time for this stop are empty, so Connection rule cannot be created.
 				 // This is valid GTFS but requires interpolation to set estimated stop times.
-				 return done(new Error(`ERROR: Empty arrival and departure times found for trip ${stopTime['trip_id']} on stop ${stopTime['stop_id']}. Interpolation is required in a previous step to handle these cases.`));
+				 console.error(`WARNING: Empty arrival and departure times found for trip ${stopTime['trip_id']} on stop ${stopTime['stop_id']}. Interpolation is required in a previous step to handle these cases (not supported yet). This stop time will be skipped.`)
+				 done();
 			 }
  
 			 // Get related trip, route and service dates
diff --git a/package-lock.json b/package-lock.json
index a545053..ca5525e 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -1,12 +1,12 @@
 {
   "name": "gtfs2lc",
-  "version": "2.1.5",
+  "version": "2.1.6",
   "lockfileVersion": 2,
   "requires": true,
   "packages": {
     "": {
       "name": "gtfs2lc",
-      "version": "2.1.5",
+      "version": "2.1.6",
       "license": "MIT",
       "dependencies": {
         "commander": "^4.1.1",
diff --git a/package.json b/package.json
index 1876a94..890ee81 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
   "name": "gtfs2lc",
-  "version": "2.1.5",
+  "version": "2.1.6",
   "description": "Mapping script from gtfs to (linked) connections",
   "main": "lib/gtfs2lc.js",
   "bin": {