diff --git a/geojson.c b/geojson.c
index 35f06c0..19ef9fa 100644
--- a/geojson.c
+++ b/geojson.c
@@ -902,6 +902,84 @@ void *run_sort(void *v) {
 	return NULL;
 }
 
+void do_read_parallel(char *map, long long len, long long initial_offset, const char *reading, struct reader *reader, volatile long long *progress_seq, struct pool *exclude, struct pool *include, int exclude_all, char *fname, int maxzoom, int basezoom, int source, int nlayers, double droprate, int *initialized, unsigned *initial_x, unsigned *initial_y) {
+	long long segs[CPUS + 1];
+	segs[0] = 0;
+	segs[CPUS] = len;
+
+	int i;
+	for (i = 1; i < CPUS; i++) {
+		segs[i] = len * i / CPUS;
+
+		while (segs[i] < len && map[segs[i]] != '\n') {
+			segs[i]++;
+		}
+	}
+
+	long long layer_seq[CPUS];
+	for (i = 0; i < CPUS; i++) {
+		// To preserve feature ordering, unique id for each segment
+		// begins with that segment's offset into the input
+		layer_seq[i] = segs[i] + initial_offset;
+	}
+
+	struct parse_json_args pja[CPUS];
+	pthread_t pthreads[CPUS];
+
+	for (i = 0; i < CPUS; i++) {
+		pja[i].jp = json_begin_map(map + segs[i], segs[i + 1] - segs[i]);
+		pja[i].reading = reading;
+		pja[i].layer_seq = &layer_seq[i];
+		pja[i].progress_seq = progress_seq;
+		pja[i].metapos = &reader[i].metapos;
+		pja[i].geompos = &reader[i].geompos;
+		pja[i].indexpos = &reader[i].indexpos;
+		pja[i].exclude = exclude;
+		pja[i].include = include;
+		pja[i].exclude_all = exclude_all;
+		pja[i].metafile = reader[i].metafile;
+		pja[i].geomfile = reader[i].geomfile;
+		pja[i].indexfile = reader[i].indexfile;
+		pja[i].poolfile = reader[i].poolfile;
+		pja[i].treefile = reader[i].treefile;
+		pja[i].fname = fname;
+		pja[i].maxzoom = maxzoom;
+		pja[i].basezoom = basezoom;
+		pja[i].layer = source < nlayers ? source : 0;
+		pja[i].droprate = droprate;
+		pja[i].file_bbox = reader[i].file_bbox;
+		pja[i].segment = i;
+		pja[i].initialized = &initialized[i];
+		pja[i].initial_x = &initial_x[i];
+		pja[i].initial_y = &initial_y[i];
+
+		if (pthread_create(&pthreads[i], NULL, run_parse_json, &pja[i]) != 0) {
+			perror("pthread_create");
+			exit(EXIT_FAILURE);
+		}
+	}
+
+	for (i = 0; i < CPUS; i++) {
+		void *retval;
+
+		if (pthread_join(pthreads[i], &retval) != 0) {
+			perror("pthread_join");
+		}
+
+		free(pja[i].jp->source);
+		json_end(pja[i].jp);
+	}
+}
+
+void start_parsing(int fd, long long offset, volatile int *is_parsing, pthread_t *previous_reader) {
+#if 0
+	if (pthread_create(previous_reader, NULL, run_start_parsing, start_parsing_args) == 0) {
+		perror("pthread_create");
+		exit(EXIT_FAILURE);
+	}
+#endif
+}
+
 int read_json(int argc, char **argv, char *fname, const char *layername, int maxzoom, int minzoom, int basezoom, double basezoom_marker_width, sqlite3 *outdb, struct pool *exclude, struct pool *include, int exclude_all, double droprate, int buffer, const char *tmpdir, double gamma, char *prevent, char *additional, int read_parallel) {
 	int ret = EXIT_SUCCESS;
 
@@ -1048,71 +1126,10 @@ int read_json(int argc, char **argv, char *fname, const char *layername, int max
 		}
 
 		if (map != NULL && map != MAP_FAILED) {
-			long long segs[CPUS + 1];
-			segs[0] = 0;
-			segs[CPUS] = st.st_size - off;
+			do_read_parallel(map, st.st_size - off, 0, reading, reader, &progress_seq, exclude, include, exclude_all, fname, maxzoom, basezoom, source, nlayers, droprate, initialized, initial_x, initial_y);
 
-			int i;
-			for (i = 1; i < CPUS; i++) {
-				segs[i] = off + (st.st_size - off) * i / CPUS;
-
-				while (segs[i] < st.st_size && map[segs[i]] != '\n') {
-					segs[i]++;
-				}
-			}
-
-			long long layer_seq[CPUS];
-			for (i = 0; i < CPUS; i++) {
-				// To preserve feature ordering, unique id for each segment
-				// begins with that segment's offset into the input
-				layer_seq[i] = segs[i];
-			}
-
-			struct parse_json_args pja[CPUS];
-			pthread_t pthreads[CPUS];
-
-			for (i = 0; i < CPUS; i++) {
-				pja[i].jp = json_begin_map(map + segs[i], segs[i + 1] - segs[i]);
-				pja[i].reading = reading;
-				pja[i].layer_seq = &layer_seq[i];
-				pja[i].progress_seq = &progress_seq;
-				pja[i].metapos = &reader[i].metapos;
-				pja[i].geompos = &reader[i].geompos;
-				pja[i].indexpos = &reader[i].indexpos;
-				pja[i].exclude = exclude;
-				pja[i].include = include;
-				pja[i].exclude_all = exclude_all;
-				pja[i].metafile = reader[i].metafile;
-				pja[i].geomfile = reader[i].geomfile;
-				pja[i].indexfile = reader[i].indexfile;
-				pja[i].poolfile = reader[i].poolfile;
-				pja[i].treefile = reader[i].treefile;
-				pja[i].fname = fname;
-				pja[i].maxzoom = maxzoom;
-				pja[i].basezoom = basezoom;
-				pja[i].layer = source < nlayers ? source : 0;
-				pja[i].droprate = droprate;
-				pja[i].file_bbox = reader[i].file_bbox;
-				pja[i].segment = i;
-				pja[i].initialized = &initialized[i];
-				pja[i].initial_x = &initial_x[i];
-				pja[i].initial_y = &initial_y[i];
-
-				if (pthread_create(&pthreads[i], NULL, run_parse_json, &pja[i]) != 0) {
-					perror("pthread_create");
-					exit(EXIT_FAILURE);
-				}
-			}
-
-			for (i = 0; i < CPUS; i++) {
-				void *retval;
-
-				if (pthread_join(pthreads[i], &retval) != 0) {
-					perror("pthread_join");
-				}
-
-				free(pja[i].jp->source);
-				json_end(pja[i].jp);
+			if (munmap(map, st.st_size - off) != 0) {
+				perror("munmap source file");
 			}
 		} else {
 			FILE *fp = fdopen(fd, "r");
@@ -1122,10 +1139,84 @@ int read_json(int argc, char **argv, char *fname, const char *layername, int max
 				continue;
 			}
 
-			long long layer_seq = 0;
-			json_pull *jp = json_begin_file(fp);
-			parse_json(jp, reading, &layer_seq, &progress_seq, &reader[0].metapos, &reader[0].geompos, &reader[0].indexpos, exclude, include, exclude_all, reader[0].metafile, reader[0].geomfile, reader[0].indexfile, reader[0].poolfile, reader[0].treefile, fname, maxzoom, basezoom, source < nlayers ? source : 0, droprate, reader[0].file_bbox, 0, &initialized[0], &initial_x[0], &initial_y[0]);
-			json_end(jp);
+			if (read_parallel) {
+				// Serial reading of chunks that are then parsed in parallel
+
+				char readname[strlen(tmpdir) + strlen("/read.XXXXXXXX") + 1];
+				sprintf(readname, "%s%s", tmpdir, "/read.XXXXXXXX");
+				int readfd = mkstemp(readname);
+				if (readfd < 0) {
+					perror(readname);
+					exit(EXIT_FAILURE);
+				}
+				FILE *readfp = fdopen(readfd, "w");
+				if (readfp == NULL) {
+					perror(readname);
+					exit(EXIT_FAILURE);
+				}
+				unlink(readname);
+
+				int c;
+				volatile int is_parsing = 0;
+				long long ahead = 0;
+				long long initial_offset = 0;
+				pthread_t previous_reader;
+
+				while ((c = getc(fp)) != EOF) {
+					putc(c, readfp);
+					ahead++;
+
+					if (c == '\n' && ahead > 100000 && is_parsing == 0) {
+						if (initial_offset != 0) {
+							if (pthread_join(previous_reader, NULL) != 0) {
+								perror("pthread_join");
+								exit(EXIT_FAILURE);
+							}
+						}
+
+						fclose(readfp);
+						start_parsing(readfd, initial_offset, &is_parsing, &previous_reader);
+
+						initial_offset += ahead;
+						ahead = 0;
+
+						sprintf(readname, "%s%s", tmpdir, "/read.XXXXXXXX");
+						int readfd = mkstemp(readname);
+						if (readfd < 0) {
+							perror(readname);
+							exit(EXIT_FAILURE);
+						}
+						FILE *readfp = fdopen(readfd, "w");
+						if (readfp == NULL) {
+							perror(readname);
+							exit(EXIT_FAILURE);
+						}
+						unlink(readname);
+					}
+				}
+
+				if (initial_offset != 0) {
+					if (pthread_join(previous_reader, NULL) != 0) {
+						perror("pthread_join");
+						exit(EXIT_FAILURE);
+					}
+				}
+
+				fclose(readfp);
+				start_parsing(readfd, initial_offset, &is_parsing, &previous_reader);
+
+				if (pthread_join(previous_reader, NULL) != 0) {
+					perror("pthread_join");
+				}
+			} else {
+				// Plain serial reading
+
+				long long layer_seq = 0;
+				json_pull *jp = json_begin_file(fp);
+				parse_json(jp, reading, &layer_seq, &progress_seq, &reader[0].metapos, &reader[0].geompos, &reader[0].indexpos, exclude, include, exclude_all, reader[0].metafile, reader[0].geomfile, reader[0].indexfile, reader[0].poolfile, reader[0].treefile, fname, maxzoom, basezoom, source < nlayers ? source : 0, droprate, reader[0].file_bbox, 0, &initialized[0], &initial_x[0], &initial_y[0]);
+				json_end(jp);
+			}
+
 			fclose(fp);
 		}
 	}