AGOL Analysis Drive Time Areas for California? How accurate are they?

[FionaRenton1]

I'm creating drive time areas using AGOL to our offices, but the maps seem very optimistic....especially in Southern California. I chose 20 minute drive time area using typical traffic for Tuesday at 0730 (am)PT to this office in Cerritos. See the map below.

I find it highly unlikely that you can drive from Long Beach to Cerritos in 20 minutes. Has anyone else created these drive time maps and found them useful or reliable?

At first I thought perhaps the time in AGOL was UTC (so I chose 8 hours later), but that gave an even bigger area.

[JaySandhu · Accepted solution]

A solve for Tuesday 7:30 PM time uses the historical travel times when creating the service area. Cerritos to Long Beach is about 15 miles, so a 20 minute drive seems reasonable to get there. Also note that the historical travel times are averages for all Tuesdays in the last few years and the last two has had lighter traffic due to the pandemic.

BTW, in your estimate, how long should it take to drive from Cerritos to Long Beach?

Jay Sandhu

[FionaRenton1]

Thanks. Google says 22-50 minutes in rush hour. I may try live traffic later if this is averaging two years..it will include the early Pandemic times when you could drive cross country in 27 hours and ride a bike on major freeways. Could ESRI add that this is averaging two years of traffic to the AGOL analysis metadata? I did not see it in the notes.

[FionaRenton1]

Also you must not have driven in SoCal! 20 minutes to drive 15 miles is a rarity.

[JaySandhu]

I do live in So Cal! And I understand that it sounds optimistic. We do take this feedback back to our data team and vendors for evaluation. Thanks,

Jay Sandhu

[FionaRenton1]

Thanks. 

[AlanHatakeyama · Accepted solution]

Thank you for your feedback.

One thing to keep in mind when traveling toward the facility is that the time of day that you specify is the arrival time at the facility.  So if you specify a 20 minute analysis at 7:30am that travels toward the facility, then the actual time of travel from the boundary of the area actually departs at 7:10am to arrive at the facility at 7:30am.  If you intend to depart from the boundary of the area at 7:30am and travel for 20 minutes, then you need to specify the time of day as 7:50am.  For a 7:50am analysis, the polygon you get will be smaller than that of the 7:30am analysis because there is more traffic when traveling between 7:30am-7:50am than there is when traveling between 7:10am-7:30am.

In the image you provided, it looks like Long Beach is right at the cusp of being able to take 20 minutes to get to Cerritos by 7:30am (i.e., leaving at 7:10am), which means that not all parts of Long Beach can get to your point in Cerritos at 7:30am with only 20 minutes of driving.  Also, as Jay mentions, the travel times do include some traffic observations from during the pandemic.  What time should you leave Long Beach to arrive in Cerritos right at 7:30am (you mentioned in your response to Jay the opposite direction of travel while driving in slow rush hour traffic)?

The polygon in the image you provided seems to be fairly accurate in shape, since the eastbound 91 from Gardena to Cerritos and the westbound 91 from Yorba Linda to Cerritos has fairly full speeds between 7:10am and 7:30am (the heavier traffic at this time of day is actually heading in the opposite directions leaving Cerritos).  Likewise the northbound I-110, I-710, I-605, I-5, 57, and 55 as they approach the 91 from the south (as well as the southbound I-110 between I-105 and the 91) are also fairly full speeds between 7:10am and 7:30am.  In contrast, the southbound I-710, I-5, I-605, and eastbound I-105 as they approach Norwalk have some slowing between 7:10am and 7:20am before things open up on the southbound I-605 between I-105 and the 91 between 7:20am and 7:30am.  Likewise, the southbound 57 between the 60 and 91 is also slow at this time.  All this results in the polygon being oblong in shape with quite a bit of width in the east-west direction, but more compressed in the north-south direction.

Thank you again for your feedback so far.  If you have any other feedback, please don't hesitate to let us know.

Alan

[FionaRenton1]

I really appreciate the very detailed reply. I decided to use live traffic for different times of day for now. Although this can change a bit I did not want to make it look like our offices serve a bigger area than they do. We are looking at drive times for staff (to and from offices) and for customers to our offices. 

These maps will be very useful.

Thanks!