Voice Guidance

It matters! Having a voice and choosing the right words matter. Whether it is the Voice that gets the popular vote on the acclaimed TV show or the words that capture the attention of voters on a heated political debate โ€” it matters! It is no different in the mapping industry. Today, open mobile navigation has a voice, and choosing the right words for the turn-by-turn service matters.

Verbal Instructions

The Mapzen Turn-by-Turn service is mobile focused, and it is essential to have verbal instructions that will work well with various text-to-speech(TTS) engines. Depending on the maneuver, we return textual instructions as well as up to three verbal instructions. These include the following:

  • The verbal transition alert instruction is intended to provide advance notice of an impending maneuver โ€“ kind of a wake up call to get the user prepared to make a maneuver.
  • The verbal pre transition instruction is more detailed and is presented just before the maneuver is made.
  • The verbal post transition instruction describes what to do after making the maneuver - usually something like continue for some distance, but can also identify if the road name changes.

Maneuver Instructions Example:

Maneuver ItemValue
instructionTurn right onto East Chocolate Avenue/US 422. Continue on US 422.
verbal_transition_alert_instructionTurn right onto East Chocolate Avenue.
verbal_pre_transition_instructionTurn right onto East Chocolate Avenue, U.S. 4 22.
verbal_post_transition_instructionContinue on U.S. 4 22 for 3.3 miles.

TTS Enhancements

Another objective of this service is to provide TTS enhancements that mimic how people actually answer when giving verbal directions. We format or expand route names so they are spoken correctly. The TTS enhancements can be implemented based on location. Since the United States’ road network is large and diverse, we chose this region and selected several examples from different states.

For US routes, we transform US to U.S. so it is pronounced as U S and not as the pronoun us or the expanded United States.

US 1 NorthU.S. 1 NorthUnited States
US 22 EastU.S. 22 EastUnited States

For state routes, we expand abbreviations - for the first example below, MA 3 South will be expanded to Massachusetts 3 South so it will not be pronounced as Maw three South.

MA 3 SouthMassachusetts 3 SouthUnited States
MD 32 WestMaryland 32 WestUnited States

For route numbers and house numbers, we group and format the numbers so they will be pronounced properly. For numbers greater than two digits, the numbers are transformed into groups of two, from right to left. In the example below, the interstate number 695 is transformed to 6 95, so it will be pronounced six ninety-five instead of six hundred ninety-five.


Similarly, the four digit state route 1021 is transformed to 10 21, so it will be pronounced ten twenty-one instead of one thousand twenty-one. When the numbers are grouped by two, any leading zero will become the letter o. Therefore, the US route 101 is transformed to 1 o1, so it will be pronounced one oh one instead of one hundred one. For any number that ends with a double zero, the double zero is transformed to hundred. The house number 7700 below is transformed to 77 hundred, so it will not be pronounced as seven thousand seven hundred. In the final example below, notice how the house number 905 is transformed to 9 o5, however the street name 203rd does not need changed because it is already properly formatted for verbal directions.

I 695 WestInterstate 6 95 WestUnited States
SR 1021State Route 10 21United States
US 101 NorthU.S. 1 o1 NorthUnited States
7700 Mapzen Way77 hundred Mapzen WayUnited States
905 203rd Street9 o5 203rd StreetUnited States

The examples below represent location specific interpretations. The first two examples demonstrate the difference between interpreting the route name as either a state abbreviation or as a county road. The third example represents a route specific to the state of Texas.

CO 7Colorado 7Colorado, United States
Co 7County Road 7Ohio, United States
FM 1018Farm to Market Road 10 18Texas, United States

Multi-cue Instructions

The Mapzen Turn-by-Turn service will detect short maneuvers and combine separate verbal instructions into one multi-cue instruction so the user will be prepared for each transition. The following example illustrates how in the 2nd maneuver we append the verbal pre transition instruction with the next verbal transition alert instruction.

voice guidance

Enhancements like these matter because it matters what you say and how you say it. Every turn-by-turn service has something to say โ€“ we just strive to say it better! You can hear the voice guidance in Eraser Map, our privacy-focused Android application.

Check out the Mapzen Turn-by-Turn documentation and let us know if you have any questions.