What cross-cutting trip data from five cities in the U.S. tells us about the overarching tendencies to make shorter and longer daily trips
One of the biggest advancements allowed by trip information collected through big data is the affordance of 24-hour tracking. Analyzing trip distance trends throughout the day for a typical weekday can reveal critical information about overall mobility trends and commuting patterns. Our analysis thus concentrates on two dimensions: the spatial (through zone distinctions) and temporal (developments over time).
If further investigated, this type of data could supplement critical planning decisions. For example, learning that short trips happen more frequently during lunchtime in downtown areas can prompt city councils to invest in infrastructure for alternative travel modes in order to alleviate the energy and time cost burden placed by car traffic. At the same time, the understanding that trip distances made to and from a city’s university zone is higher than the average for similar zones in other cities can alert planners to the need to increase student housing options in that area.
In the following analysis, zone distinctions were based on a number of factors. For each of the five cities under study (namely, Seattle, Denver, Los Angeles, Austin and Savannah), areas associated with distinctive socio-economic profiles and their corresponding travel patterns were identified to create a basis for studying movements in and out of -and between- these articulated zones. The fixed zone typologies identified for each city were two attractor typologies (downtown and university areas) and two generator typologies (high-income and suburban residential areas). These classified zones correspond to a careful synthesis between census-based boundaries and morphological features. The boundary-setting of each zone took into consideration existing physical barriers (such as highways, natural barriers, etc.) and functional organization differences such that each zone is a functional class of its own (e.g. residential, industrial, mixed-use), practically functioning as a continuous and homogeneous area.
Aggregate Mobility Trends
Despite contextual variances, it is interesting that trip profiles for each distance category (shortest: 0-1 miles to longest: 10-20 miles) have very similar trends in all cities throughout the day; as we move from short to long trips, the peak point in the graph gradually moves from center to ends. This means that the percentage of short trips are highest in the middle of the day while longer trips are more concentrated in morning and evening hours. The same trend holds for trip times. However, shorter trip times are more concentrated towards the evening segment of the day as opposed to midday. Trips travelled in Los Angeles and Austin tend to be longer in distance on average, while Los Angeles reserves the highest average trip time of the five cities. Savannah, on the other hand, being a much smaller city, maintains the lowest average trip time. A deeper look at internal variances by city zone allows us to distinguish further trends.
A zone-based analysis of average daily travel distances in each city exposes some pattern distinctions. Furthermore, it confirms the recurring phenomenon of longer distances travelled in the morning hours in all areas, whereas the afternoon trip concentration is more widespread. Additionally, the analysis shows that the greatest concentration of trips does not necessarily correspond to trips made to and from downtown areas in all cities. Though we expect that downtown trips are highest in length, since they attract more movements from farther away, the data reveals that this is only the case in the cities of Seattle and Los Angeles.
Looking specifically at short trips (those falling in the range of 0-2 miles), we deduce that the highest percentage of short trips occur in the midday hours, i.e. during lunchtime. Spatially, we see that this increase is less accentuated in residential areas than it is in downtown and university areas. To take an example, short trips in Seattle increase by factors of 2 and 3 in residential areas during lunchtime, whereas in university and downtown zones they multiply by factors of 5 and 7, respectively. In Austin’s university district, almost 50% of trips made during lunchtime are short trips, pointing to a high transformative potential to non-motorized transport.
A comparative assessment of short, medium and long trips by zone reveals that downtowns have a higher concentration of short (0-2 miles) and long trips (10 miles and more) than other areas. Mid-length movements (2-10 miles) are conversely more pronounced in the residential zones, accounting for more than half of all trips in all five cities.
Studying the relationship between typical trip duration and diverse population groups can help us understand the positionality of each group based on their income levels. This also includes looking at where people of different income groups live to understand how urban form affects trip times.
Taking a closer look at the demographic distribution, we find that there are some clear correlations between certain socio-economic profiles of travelers and trip time distribution. Data shows that in most studied cities, longer trip times tend to be associated with larger households, lower-income households, and a high private modal share in these respective areas. In other words, with a few exceptions, trips tend to be longer for travelers from large household sizes, of lower income groups and in cities that rely most highly on private car trips. While the first two elements may be linked to suburbanization and longer trips travelled between the suburbs and the city (high trip time due to distance), the third trait may indicate car-induced traffic (high trip times due to congestion). Population groups in these categories are particularly time-deprived with respect to their counterparts.
Moreover, city data analysis shows us that there is a negative correlation between trip times and younger travelers – particularly part of the millennial age group (20-29 years old) – as well as people living in areas with high population density, and high active modal shares. In line with the ‘Back to Downtown’ mobility trend, data shows that younger people who are more likely to live in the city and not be tied to larger families, are more likely to enjoy lower travel times. At the same time, almost counter-intuitively, travelers living in high-density areas travel faster. This could simply be due to home-work proximity, since jobs are mostly concentrated in dense city centers, and the wider offering of various transport modes in busy areas. In the same vein, high-density areas make travelling by active modes such as walking and cycling easier given the proximity of destinations and the higher degree of walkability owing to inner-city planning.
Out of the five cities, Los Angeles seems to stand in clear contradiction to the general trend on several accounts. In Los Angeles, travel times tend to increase with all factors, save active modal share with which there is no correlation. It is interesting to note that even younger travelers and high-density populations are more likely to sustain longer travel times. However, due to the polycentric morphology of Los Angeles city, movement patterns are more spatially varied than the other cities under study. With Denver as well, another polycentric city, there is no correlation between population density and travel times.
Takwimu za safari kutoka miji mitano nchini Marekani zinatuambia juu ya mwelekeo wa kufanya safari fupi na ndefu zaidi za kila siku. Uchambuzi wa mwenendo wa umbali wa safari siku nzima kwa siku ya kawaida ya wiki inaweza kufunua habari muhimu juu ya mwenendo wa jumla wa uhamaji na mifumo ya kusafiri. Kwa hiyo uchambuzi wetu unazingatia vipimo viwili: vya kijiografia (kupitia tofauti za eneo) na vya muda (maendeleo kwa muda). Ikiwa itachunguzwa zaidi, aina hii ya data inaweza kuongeza maamuzi muhimu ya mipango. Kwa mfano, kujifunza kwamba safari fupi hutokea mara nyingi wakati wa chakula cha mchana katika maeneo ya katikati ya mji inaweza kuchochea halmashauri za mji kuwekeza katika miundombinu kwa njia mbadala za kusafiri ili kupunguza mzigo wa gharama za nishati na wakati uliowekwa na trafiki ya gari. Wakati huo huo, ufahamu kwamba umbali wa safari kufanywa kwa na kutoka eneo la chuo kikuu cha mji ni juu kuliko wastani kwa maeneo sawa katika miji mingine inaweza kuwaonya wapangaji wa mahitaji ya kuongeza chaguzi za makazi ya wanafunzi katika eneo hilo. Katika uchambuzi ufuatao, tofauti za eneo zilitegemea mambo kadhaa. Kwa kila moja ya miji mitano iliyochunguzwa (yaani, Seattle, Denver, Los Angeles, Austin na Savannah), maeneo yanayohusiana na maelezo ya kipekee ya kijamii na kiuchumi na mifumo yao ya kusafiri ilitambuliwa ili kuunda msingi wa kusoma harakati ndani na nje ya - na kati ya - maeneo haya yaliyoelezwa. Aina ya eneo la kudumu iliyotambuliwa kwa kila mji ilikuwa aina mbili za kivutio (maeneo ya katikati ya mji na chuo kikuu) na aina mbili za jenereta (maeneo ya makazi ya mapato ya juu na vitongoji). Maeneo haya yaliyoainishwa yanalingana na mchanganyiko wa uangalifu kati ya mipaka ya sensa na sifa za kimaumbile. Mpaka-kuweka ya kila eneo alichukua kuzingatia vizuizi zilizopo kimwili (kama vile barabara kuu, vizuizi vya asili, nk.) tofauti za shirika na kazi kama kwamba kila eneo ni darasa kazi ya yake mwenyewe (kwa mfano makazi, viwanda, matumizi mchanganyiko), kufanya kazi kwa kweli kama eneo kuendelea na homogeneous. "Hata hivyo, kwa sababu ya tofauti za muktadha, ni muhimu kutambua kwamba ""maelezo ya safari kwa kila aina ya umbali (mfupi: 0-1 maili hadi ndefu: 10-20 maili) yana mwelekeo sawa katika miji yote kwa siku nzima; kama tunaendelea kutoka safari fupi hadi safari ndefu, hatua ya kilele katika grafu hatua kwa hatua inahama kutoka katikati hadi mwisho." Hii inamaanisha kuwa asilimia ya safari fupi ni ya juu zaidi katikati ya siku wakati safari ndefu zinazingatia zaidi asubuhi na jioni. Mwelekeo huohuo unatumika kwa nyakati za safari. Hata hivyo, muda mfupi wa safari ni zaidi umakini kuelekea sehemu ya jioni ya siku kama kinyume na adhuhuri. Safari zilizosafiri katika Los Angeles na Austin huwa na umbali mrefu zaidi kwa wastani, wakati Los Angeles inahifadhi muda wa safari ya wastani wa juu zaidi ya miji mitano. Savannah, kwa upande mwingine, kuwa mji mdogo zaidi, huhifadhi muda wa chini zaidi wa safari ya wastani. Kutazama kwa undani tofauti za ndani kwa eneo la jiji huturuhusu kutofautisha mwenendo zaidi. Uchambuzi wa eneo-msingi wa wastani wa umbali wa kusafiri kwa siku katika kila mji hufunua baadhi ya tofauti za muundo. Kwa kuongezea, inathibitisha hali ya mara kwa mara ya umbali mrefu zaidi uliosafiri katika masaa ya asubuhi katika maeneo yote, wakati mkusanyiko wa safari ya alasiri ni wa kuenea zaidi. Kwa kuongezea, uchambuzi unaonyesha kwamba mkusanyiko mkubwa wa safari haufanani lazima na safari zilizofanywa kwenda na kutoka maeneo ya katikati mwa jiji katika miji yote. Ingawa tunatarajia kwamba safari za katikati mwa jiji ni ndefu zaidi, kwa kuwa zinavutia harakati zaidi kutoka mbali zaidi, data zinafunua kwamba hii ni kesi tu katika miji ya Seattle na Los Angeles. Kwa kuzingatia safari fupi (ambazo huanguka katika safu ya maili 0-2) tunagundua kwamba asilimia ya juu ya safari fupi hutokea katika masaa ya mchana. wakati wa chakula cha mchana. Kwa kijiografia, tunaona kwamba ongezeko hili halionyeshwi sana katika maeneo ya makazi kuliko katika maeneo ya katikati ya jiji na ya chuo kikuu. Kwa mfano, safari fupi za kwenda Seattle huongezeka kwa mara mbili na tatu katika maeneo ya makazi wakati wa chakula cha mchana, wakati katika vyuo vikuu na maeneo ya katikati ya jiji huongezeka kwa mara tano na saba. Katika wilaya ya chuo kikuu cha Austin, karibu 50% ya safari zilizofanywa wakati wa chakula cha mchana ni safari fupi, ikionyesha uwezekano mkubwa wa mabadiliko kwa usafiri usio na injini. Uhakiki wa kulinganisha safari fupi, za kati na ndefu kwa eneo unaonyesha kuwa vituo vya jiji vina mkusanyiko mkubwa wa safari fupi (0-2 maili) na safari ndefu (maili 10 na zaidi) kuliko maeneo mengine. Kwa upande mwingine, safari za umbali wa kati (maili 2 hadi 10) ni kubwa zaidi katika maeneo ya makazi, na zinawakilisha zaidi ya nusu ya safari zote katika miji yote mitano. Kujifunza uhusiano kati ya muda wa kawaida wa safari na makundi mbalimbali ya watu inaweza kutusaidia kuelewa positionality ya kila kundi kulingana na viwango vya mapato yao. Hii pia inajumuisha kuangalia ambapo watu wa makundi tofauti ya mapato wanaishi kuelewa jinsi fomu ya mijini inaathiri muda wa safari. Kwa kuzingatia kwa karibu usambazaji wa idadi ya watu, tunapata kuwa kuna baadhi ya uhusiano wa wazi kati ya maelezo fulani ya kijamii na kiuchumi ya wasafiri na usambazaji wa muda wa safari. Takwimu zinaonyesha kwamba katika miji mingi iliyochunguzwa, muda mrefu wa safari huelekea kuhusishwa na kaya kubwa, nyumba za mapato ya chini, na sehemu ya juu ya njia binafsi katika maeneo haya. Kwa maneno mengine, isipokuwa chache, safari huwa ndefu zaidi kwa wasafiri kutoka kwa ukubwa mkubwa wa kaya, wa vikundi vya mapato ya chini na katika miji ambayo hutegemea zaidi safari za gari binafsi. Ingawa mambo mawili ya kwanza yanaweza kuhusishwa na suburbanization na safari ndefu zilizosafiri kati ya vitongoji na mji (wakati wa safari ya juu kwa sababu ya umbali), tabia ya tatu inaweza kuonyesha trafiki ya gari (wakati wa safari ya juu kwa sababu ya msongamano). Vikundi vya watu katika makundi haya ni hasa wakati-kupunguzwa kuhusiana na wenzao. Zaidi ya hayo, uchambuzi wa data ya mji unaonyesha kwamba kuna uhusiano hasi kati ya muda wa safari na wasafiri vijana - hasa sehemu ya kikundi cha umri wa milenia (20-29 miaka) - pamoja na watu wanaoishi katika maeneo yenye wiani wa idadi ya watu, na hisa za hali ya juu. Kwa mujibu wa mwelekeo wa "Back to Downtown" uhamaji, data inaonyesha kwamba vijana ambao ni zaidi uwezekano wa kuishi katika mji na si kushikamana na familia kubwa, ni zaidi uwezekano wa kufurahia muda mfupi wa kusafiri. Wakati huohuo, karibu kinyume cha hisia, wasafiri wanaoishi katika maeneo yenye watu wengi husafiri haraka zaidi. Hii inaweza tu kuwa kutokana na ukaribu wa nyumbani-kazi, kwani kazi ni zaidi ya kujikita katika vituo vya miji yenye msongamano, na kutoa pana ya aina mbalimbali za usafiri katika maeneo ya shughuli nyingi. Kwa njia hiyo hiyo, maeneo yenye msongamano mkubwa hufanya kusafiri kwa njia za kazi kama vile kutembea na baiskeli iwe rahisi kwa sababu ya ukaribu wa maeneo na kiwango cha juu cha kutembea kwa sababu ya mipango ya ndani ya mji. Kati ya miji mitano, Los Angeles inaonekana kusimama katika kinyume wazi na mwelekeo wa jumla juu ya akaunti kadhaa. Katika Los Angeles, muda wa kusafiri huwa na kuongezeka na sababu zote, kuokoa kushiriki modal hai ambayo hakuna uhusiano. Ni muhimu kutambua kwamba hata wasafiri vijana na watu wenye idadi kubwa ya watu wana uwezekano mkubwa wa kudumu kwa muda mrefu zaidi. Hata hivyo, kwa sababu ya morphology polycentric ya mji wa Los Angeles, mifumo ya harakati ni zaidi spatially tofauti kuliko miji mingine chini ya utafiti. Kwa Denver pia, jiji jingine lenye makazi mengi, hakuna uhusiano kati ya wiani wa idadi ya watu na muda wa kusafiri.