Hi,

My goal is to estimate arrival times of buses at bus stops where historical GPS data for each bus is available and real-time bus location is available for each bus. What I would like to do is use the historical data to determine the mean time (in seconds) and SD taken for a bus to travel from each stop to its next stop. No problem doing this.

Now, if the bus stops are number from 1 to N, and I know the mean time and SD for a bus to travel from stop s to stop s+1 for all s (in range 1 to N-1), then if the bus is at stop 4 I can can predict the time time needed for the bus to arrive at stop 8 by adding the mean times for the segments 4-5, 5-6, 6-7, and 7-8. My question is, how do I calculate the SD for the bus trip from stop 4 to 8 given the SD for each of the segments (4-5, 5-6, 6-7, and 7-8)?

Please keep in mind that the sample sizes used to calculate the mean time and SD from stop-to-stop will be exactly the same for every segment (stop-to-stop).

Thank you in advance for any assistance you can offer.

Regards,

Matt

My goal is to estimate arrival times of buses at bus stops where historical GPS data for each bus is available and real-time bus location is available for each bus. What I would like to do is use the historical data to determine the mean time (in seconds) and SD taken for a bus to travel from each stop to its next stop. No problem doing this.

Now, if the bus stops are number from 1 to N, and I know the mean time and SD for a bus to travel from stop s to stop s+1 for all s (in range 1 to N-1), then if the bus is at stop 4 I can can predict the time time needed for the bus to arrive at stop 8 by adding the mean times for the segments 4-5, 5-6, 6-7, and 7-8. My question is, how do I calculate the SD for the bus trip from stop 4 to 8 given the SD for each of the segments (4-5, 5-6, 6-7, and 7-8)?

Please keep in mind that the sample sizes used to calculate the mean time and SD from stop-to-stop will be exactly the same for every segment (stop-to-stop).

Thank you in advance for any assistance you can offer.

Regards,

Matt

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