Iterations to my board game

In our 1st week we had to think up and make a board game in 15minutes; the game I thought of was "Cops and Robbers". Cops and Robbers was a very basic game; which is played on a 36square board with various squares having instructions on them for ex: Move foward X amount of spaces.
The rules of the game is as follows :-

2-4 players
One player plays the Cops, and the other player plays the Robbers
At the start of the game each player rolls the dice to determine who goes first
Players move around the board clockwise
Cops start on the police station square; if the cops land on the robbers hideout square they raid the hideout and gain a extra turn.
Robbers start on the get away square; if the robbers land on the jail square there is a jail break and the robbers gain a extra turn.
The cops roll 2 dice for their turn (one white for moving back and one blue for moving foward; they may only choose one of the dice for their movement, and the robbers roll one dice for their movement and can only move foward.

Objective of the game:-
The Cops objective of the game is to land on the same square as the robbers; when they do this they catch the robbers and the game ends with the cops being the winners.
The Robbers objective is to go around the board 3times and to pass the hideout square after the third time round.

When I first tested this game with Rob, it wasn't fairly successful as rob lost in two turns; so I made a few changes by altering some Squares to not make the game end so fast. I then tested the game again as a 2player game and it worked really well was a very intense game of cat and mouse; So I then decided to test it with 4players and the game didn't seem to work as well as it did in two players.

I got some feedback on how to improve the game; the feedback was to make the play board bigger and to add maybe some alternative routes to provide more choice for movement. I decided to improve on this and thought about making alleyways which will lead to other squares and to include a benefit/drawbacks for using them; the benefits are that the robbers do not receive a penalty for using the alleyways and get to roll 2dice for moving forward or back; while the cops can only move forward through the alleyways. I have not yet drawn up a new board to try out how these new changes will work, but I am looking forward to testing it.