Adaptive Coordinated Variable Speed Limit between Highway Mainline and On-Ramp with Deep Reinforcement Learning

Table 1

ACVSL notation list.

No.	Notation	Explanation
1		Section count on highway part , where and refers to mainline and on-ramp, respectively.
2		Total flow through the merging bottleneck at time
3		Traffic flow of section at time
4		Error state of section on highway upstream of the merging zone at time
5		Actual traffic density on section of highway at time
6		Critical density between fluent and congested traffic flow
7		Error state of merging zone at time step
8		Actual density of merging zone at time step
9		Control parameter on section of highway at time step
10		Intended speed on VSL sign for section on highway at time step
11		Length of section on highway
12		Actual speed on section at time step
13		Theoretical speed of the merging zone from macroscopic fundamental diagram at critical density
14		Maximum speed limit demonstrated on VSL sign for section of at time step
15		Actual speed on section of highway at time step
16		Maximum speed difference in VSL between successive time steps and sections
17		Final speed delivered to VSL sign after considering the lower bound of speed limit for section on highway at time step
18		Upper bound of VSL
19		Lower bound of VSL