ArcGIS Online (AGO) does not support linear referencing/dynamic segmentation of events in tables. Linear referencing is an essential workflow in transportation organizations which store much of their data in tables that require dynamic segmentation to visualize or spatially analyze. The National Hydrography Dataset (NHD) also relies on liner referencing to place water supply and water quality features on the NHD network.
Without linear referencing support in AGO, web-based users have no access to use the power of GIS analysis on much of their enterprise tabular data. Organizations have huge investments in legacy data and data collected and stored in event tables that are not available to AGO users, only Desktop users.
This could be implemented by allowing an organization to add a Roads and Highways LRS Service to their organization, like Address Locators are handled, now. User could access the service by adding data in a spreadsheet or CSV format (like geocoding is done).