Sumo emissions are missing

[temetski]

Bug Description

PR #981 made changes to how flow generates emissions. This looks to me like emissions (in the flow sense) is essentially a datalogger of vehicle states (such as positions, headways, leader_ids, etc). SUMO, on the other hand, uses the emissions output to also dump information about vehicle emissions: NOx, PM, HC, fuel, etc.

I want to ask if SUMO's emissions are still relevant to flow in general. One particular use case I'm looking at is in the context of the impact of different vehicle types (and different emissionClasses) on vehicle emissions. If so, should 2 approaches be maintained: 1) let Sumo generate the emission files, and 2) let flow generate a custom emission file?
If 2) is the preferred direction, perhaps there should be a method that lets users pick what data to store.

The changes in #981 should have failed TestEmissionToCSV, but as this test uses a static XML as the basis for emission_to_csv, the test currently passes.

Screenshots

Screenshots:
old emissions have these headers

new emissions have different headers

Versions

• Flow version: 0.5.0.dev
• Flow commit number: 8a935a8

[temetski]

Alternatively, solving #945 also resolves this issue.